Merge branch 'pks-gittest-hash-clean' into 'master'

gittest: Refactorings to make the package hash-clean

See merge request gitlab-org/gitaly!4734

54 files changed, 256 insertions, 281 deletions

diff --git a/cmd/gitaly-git2go-v15/cherry_pick_test.go b/cmd/gitaly-git2go-v15/cherry_pick_test.go
index e9b82c8db..129476451 100644
--- a/cmd/gitaly-git2go-v15/cherry_pick_test.go
+++ b/cmd/gitaly-git2go-v15/cherry_pick_test.go
@@ -148,7 +148,7 @@ func TestCherryPick(t *testing.T) {
 		testcfg.BuildGitalyGit2Go(t, cfg)
 		executor := buildExecutor(t, cfg)
 
-		base := gittest.WriteCommit(t, cfg, repoPath, gittest.WithParents(), gittest.WithTreeEntries(tc.base...))
+		base := gittest.WriteCommit(t, cfg, repoPath, gittest.WithTreeEntries(tc.base...))
 
 		ours, commit := "nonexistent", "nonexistent"
 		if len(tc.ours) > 0 {
@@ -229,7 +229,6 @@ func TestCherryPickStructuredErrors(t *testing.T) {
 		t,
 		cfg,
 		repoPath,
-		gittest.WithParents(),
 		gittest.WithTreeEntries(gittest.TreeEntry{
 			Path: "file", Content: "foo", Mode: "100644",
 		}))
diff --git a/cmd/gitaly-git2go-v15/conflicts_test.go b/cmd/gitaly-git2go-v15/conflicts_test.go
index 4ab3e4de3..c8e9848eb 100644
--- a/cmd/gitaly-git2go-v15/conflicts_test.go
+++ b/cmd/gitaly-git2go-v15/conflicts_test.go
@@ -172,7 +172,7 @@ func TestConflicts(t *testing.T) {
 
 		testcfg.BuildGitalyGit2Go(t, cfg)
 
-		base := gittest.WriteCommit(t, cfg, repoPath, gittest.WithParents(), gittest.WithTreeEntries(tc.base...))
+		base := gittest.WriteCommit(t, cfg, repoPath, gittest.WithTreeEntries(tc.base...))
 		ours := gittest.WriteCommit(t, cfg, repoPath, gittest.WithParents(base), gittest.WithTreeEntries(tc.ours...))
 		theirs := gittest.WriteCommit(t, cfg, repoPath, gittest.WithParents(base), gittest.WithTreeEntries(tc.theirs...))
 
@@ -193,7 +193,7 @@ func TestConflicts(t *testing.T) {
 
 func TestConflicts_checkError(t *testing.T) {
 	cfg, repo, repoPath := testcfg.BuildWithRepo(t)
-	base := gittest.WriteCommit(t, cfg, repoPath, gittest.WithParents(), gittest.WithTreeEntries())
+	base := gittest.WriteCommit(t, cfg, repoPath, gittest.WithTreeEntries())
 	validOID := glgit.ObjectID(base.String())
 	executor := buildExecutor(t, cfg)
 
diff --git a/cmd/gitaly-git2go-v15/merge_test.go b/cmd/gitaly-git2go-v15/merge_test.go
index 9f1919464..00c3b0ee3 100644
--- a/cmd/gitaly-git2go-v15/merge_test.go
+++ b/cmd/gitaly-git2go-v15/merge_test.go
@@ -289,7 +289,7 @@ func TestMerge_trees(t *testing.T) {
 		testcfg.BuildGitalyGit2Go(t, cfg)
 		executor := buildExecutor(t, cfg)
 
-		base := gittest.WriteCommit(t, cfg, repoPath, gittest.WithParents(), gittest.WithTreeEntries(tc.base...))
+		base := gittest.WriteCommit(t, cfg, repoPath, gittest.WithTreeEntries(tc.base...))
 		ours := gittest.WriteCommit(t, cfg, repoPath, gittest.WithParents(base), gittest.WithTreeEntries(tc.ours...))
 		theirs := gittest.WriteCommit(t, cfg, repoPath, gittest.WithParents(base), gittest.WithTreeEntries(tc.theirs...))
 
@@ -362,7 +362,7 @@ func TestMerge_squash(t *testing.T) {
 	theirFile1 := gittest.TreeEntry{Path: "file.txt", Content: "b\nc\nd", Mode: "100644"}
 	theirFile2 := gittest.TreeEntry{Path: "file.txt", Content: "b\nc\nd\ne", Mode: "100644"}
 
-	base := gittest.WriteCommit(t, cfg, repoPath, gittest.WithParents(), gittest.WithTreeEntries(baseFile))
+	base := gittest.WriteCommit(t, cfg, repoPath, gittest.WithTreeEntries(baseFile))
 	ours := gittest.WriteCommit(t, cfg, repoPath, gittest.WithParents(base), gittest.WithTreeEntries(ourFile))
 	theirs1 := gittest.WriteCommit(t, cfg, repoPath, gittest.WithParents(base), gittest.WithTreeEntries(theirFile1))
 	theirs2 := gittest.WriteCommit(t, cfg, repoPath, gittest.WithParents(theirs1), gittest.WithTreeEntries(theirFile2))
@@ -420,7 +420,7 @@ func TestMerge_recursive(t *testing.T) {
 
 	repoProto, repoPath := gittest.InitRepo(t, cfg, cfg.Storages[0])
 
-	base := gittest.WriteCommit(t, cfg, repoPath, gittest.WithParents(), gittest.WithTreeEntries(
+	base := gittest.WriteCommit(t, cfg, repoPath, gittest.WithTreeEntries(
 		gittest.TreeEntry{Path: "base", Content: "base\n", Mode: "100644"},
 	))
 
diff --git a/cmd/gitaly-git2go-v15/rebase_test.go b/cmd/gitaly-git2go-v15/rebase_test.go
index d6cce487b..38de7af42 100644
--- a/cmd/gitaly-git2go-v15/rebase_test.go
+++ b/cmd/gitaly-git2go-v15/rebase_test.go
@@ -246,7 +246,7 @@ func TestRebase_skipEmptyCommit(t *testing.T) {
 	// Set up history with two diverging lines of branches, where both sides have implemented
 	// the same changes. During rebase, the diff will thus become empty.
 	base := gittest.WriteCommit(t, cfg, repoPath,
-		gittest.WithParents(), gittest.WithTreeEntries(gittest.TreeEntry{
+		gittest.WithTreeEntries(gittest.TreeEntry{
 			Path: "a", Content: "base", Mode: "100644",
 		}),
 	)
diff --git a/cmd/gitaly-git2go-v15/revert_test.go b/cmd/gitaly-git2go-v15/revert_test.go
index 4b885c0e8..35a603ba9 100644
--- a/cmd/gitaly-git2go-v15/revert_test.go
+++ b/cmd/gitaly-git2go-v15/revert_test.go
@@ -86,7 +86,7 @@ func TestRevert_trees(t *testing.T) {
 		{
 			desc: "trivial revert succeeds",
 			setupRepo: func(t testing.TB, cfg config.Cfg, repoPath string) (ours, revert string) {
-				baseOid := gittest.WriteCommit(t, cfg, repoPath, gittest.WithParents(), gittest.WithTreeEntries(
+				baseOid := gittest.WriteCommit(t, cfg, repoPath, gittest.WithTreeEntries(
 					gittest.TreeEntry{Path: "a", Content: "apple", Mode: "100644"},
 					gittest.TreeEntry{Path: "b", Content: "banana", Mode: "100644"},
 				))
@@ -113,7 +113,7 @@ func TestRevert_trees(t *testing.T) {
 		{
 			desc: "conflicting revert fails",
 			setupRepo: func(t testing.TB, cfg config.Cfg, repoPath string) (ours, revert string) {
-				baseOid := gittest.WriteCommit(t, cfg, repoPath, gittest.WithParents(), gittest.WithTreeEntries(
+				baseOid := gittest.WriteCommit(t, cfg, repoPath, gittest.WithTreeEntries(
 					gittest.TreeEntry{Path: "a", Content: "apple", Mode: "100644"},
 				))
 				revertOid := gittest.WriteCommit(t, cfg, repoPath, gittest.WithParents(baseOid), gittest.WithTreeEntries(
@@ -131,7 +131,7 @@ func TestRevert_trees(t *testing.T) {
 		{
 			desc: "empty revert fails",
 			setupRepo: func(t testing.TB, cfg config.Cfg, repoPath string) (ours, revert string) {
-				baseOid := gittest.WriteCommit(t, cfg, repoPath, gittest.WithParents(), gittest.WithTreeEntries(
+				baseOid := gittest.WriteCommit(t, cfg, repoPath, gittest.WithTreeEntries(
 					gittest.TreeEntry{Path: "a", Content: "apple", Mode: "100644"},
 				))
 				revertOid := gittest.WriteCommit(t, cfg, repoPath, gittest.WithParents(baseOid), gittest.WithTreeEntries(
@@ -149,7 +149,7 @@ func TestRevert_trees(t *testing.T) {
 		{
 			desc: "nonexistent ours fails",
 			setupRepo: func(t testing.TB, cfg config.Cfg, repoPath string) (ours, revert string) {
-				revertOid := gittest.WriteCommit(t, cfg, repoPath, gittest.WithParents(), gittest.WithTreeEntries(
+				revertOid := gittest.WriteCommit(t, cfg, repoPath, gittest.WithTreeEntries(
 					gittest.TreeEntry{Path: "a", Content: "apple", Mode: "100644"},
 				))
 
@@ -160,7 +160,7 @@ func TestRevert_trees(t *testing.T) {
 		{
 			desc: "nonexistent revert fails",
 			setupRepo: func(t testing.TB, cfg config.Cfg, repoPath string) (ours, revert string) {
-				oursOid := gittest.WriteCommit(t, cfg, repoPath, gittest.WithParents(), gittest.WithTreeEntries(
+				oursOid := gittest.WriteCommit(t, cfg, repoPath, gittest.WithTreeEntries(
 					gittest.TreeEntry{Path: "a", Content: "apple", Mode: "100644"},
 				))
 
diff --git a/cmd/gitaly-git2go-v15/testhelper_test.go b/cmd/gitaly-git2go-v15/testhelper_test.go
index 32f646195..274687cb6 100644
--- a/cmd/gitaly-git2go-v15/testhelper_test.go
+++ b/cmd/gitaly-git2go-v15/testhelper_test.go
@@ -5,7 +5,6 @@ package main
 import (
 	"fmt"
 	"testing"
-	"time"
 
 	git "github.com/libgit2/git2go/v33"
 	"gitlab.com/gitlab-org/gitaly/v15/internal/git/gittest"
@@ -16,9 +15,9 @@ import (
 
 // DefaultAuthor is the author used by BuildCommit
 var DefaultAuthor = git.Signature{
-	Name:  "Scrooge McDuck",
-	Email: "scrooge@mcduck.com",
-	When:  time.Date(2019, 11, 3, 11, 27, 59, 0, time.FixedZone("", 60*60)),
+	Name:  gittest.DefaultCommitterName,
+	Email: gittest.DefaultCommitterMail,
+	When:  gittest.DefaultCommitTime,
 }
 
 func TestMain(m *testing.M) {
diff --git a/internal/backup/backup_test.go b/internal/backup/backup_test.go
index 0a22beaaf..99c52683c 100644
--- a/internal/backup/backup_test.go
+++ b/internal/backup/backup_test.go
@@ -424,7 +424,6 @@ func testManagerRestore(t *testing.T, ctx context.Context) {
 
 				root := gittest.WriteCommit(t, cfg, expectedRepoPath,
 					gittest.WithBranch("master"),
-					gittest.WithParents(),
 				)
 				master1 := gittest.WriteCommit(t, cfg, expectedRepoPath,
 					gittest.WithBranch("master"),
diff --git a/internal/git/catfile/object_info_reader_test.go b/internal/git/catfile/object_info_reader_test.go
index debe5562b..a4e9b3c54 100644
--- a/internal/git/catfile/object_info_reader_test.go
+++ b/internal/git/catfile/object_info_reader_test.go
@@ -182,7 +182,7 @@ func TestObjectInfoReader_queue(t *testing.T) {
 		Size: int64(len("foobar")),
 	}
 
-	commitOID := gittest.WriteCommit(t, cfg, repoPath)
+	commitOID := gittest.WriteCommit(t, cfg, repoPath, gittest.WithParents("master"))
 	commitInfo := ObjectInfo{
 		Oid:  commitOID,
 		Type: "commit",
diff --git a/internal/git/gitpipe/catfile_info_test.go b/internal/git/gitpipe/catfile_info_test.go
index 75882b5d4..ad0377d43 100644
--- a/internal/git/gitpipe/catfile_info_test.go
+++ b/internal/git/gitpipe/catfile_info_test.go
@@ -288,7 +288,7 @@ func TestCatfileInfoAllObjects(t *testing.T) {
 	tree := gittest.WriteTree(t, cfg, repoPath, []gittest.TreeEntry{
 		{Path: "foobar", Mode: "100644", OID: blob1},
 	})
-	commit := gittest.WriteCommit(t, cfg, repoPath, gittest.WithParents())
+	commit := gittest.WriteCommit(t, cfg, repoPath)
 
 	actualObjects := []CatfileInfoResult{
 		{ObjectInfo: &catfile.ObjectInfo{Oid: blob1, Type: "blob", Size: 6}},
diff --git a/internal/git/gittest/command_test.go b/internal/git/gittest/command_test.go
index 1cf52d728..2cbe8dae3 100644
--- a/internal/git/gittest/command_test.go
+++ b/internal/git/gittest/command_test.go
@@ -1,5 +1,3 @@
-//go:build !gitaly_test_sha256
-
 package gittest
 
 import (
diff --git a/internal/git/gittest/commit.go b/internal/git/gittest/commit.go
index f8902ffe4..526e73545 100644
--- a/internal/git/gittest/commit.go
+++ b/internal/git/gittest/commit.go
@@ -15,9 +15,20 @@ import (
 	"gitlab.com/gitlab-org/gitaly/v15/proto/go/gitalypb"
 )
 
-const (
-	committerName  = "Scrooge McDuck"
-	committerEmail = "scrooge@mcduck.com"
+var (
+	// DefaultCommitterName is the default name of the committer and author used to create
+	// commits.
+	DefaultCommitterName = "Scrooge McDuck"
+	// DefaultCommitterMail is the default mail of the committer and author used to create
+	// commits.
+	DefaultCommitterMail = "scrooge@mcduck.com"
+	// DefaultCommitTime is the default time used as written by WriteCommit().
+	DefaultCommitTime = time.Date(2019, 11, 3, 11, 27, 59, 0, time.FixedZone("", 60*60))
+	// DefaultCommitterSignature is the default signature in the format like it would be present
+	// in commits: "$name <$email> $unixtimestamp $timezone".
+	DefaultCommitterSignature = fmt.Sprintf(
+		"%s <%s> %d %s", DefaultCommitterName, DefaultCommitterMail, DefaultCommitTime.Unix(), DefaultCommitTime.Format("-0700"),
+	)
 )
 
 type writeCommitConfig struct {
@@ -133,12 +144,6 @@ func WriteCommit(t testing.TB, cfg config.Cfg, repoPath string, opts ...WriteCom
 	}
 	stdin := bytes.NewBufferString(message)
 
-	// The ID of an arbitrary commit known to exist in the test repository.
-	parents := []git.ObjectID{"1a0b36b3cdad1d2ee32457c102a8c0b7056fa863"}
-	if writeCommitConfig.parents != nil {
-		parents = writeCommitConfig.parents
-	}
-
 	if len(writeCommitConfig.treeEntries) > 0 && writeCommitConfig.treeID != "" {
 		require.FailNow(t, "cannot set tree entries and tree ID at the same time")
 	}
@@ -148,15 +153,15 @@ func WriteCommit(t testing.TB, cfg config.Cfg, repoPath string, opts ...WriteCom
 		tree = WriteTree(t, cfg, repoPath, writeCommitConfig.treeEntries).String()
 	} else if writeCommitConfig.treeID != "" {
 		tree = writeCommitConfig.treeID.String()
-	} else if len(parents) == 0 {
+	} else if len(writeCommitConfig.parents) == 0 {
 		// If there are no parents, then we set the root tree to the empty tree.
 		tree = DefaultObjectHash.EmptyTreeOID.String()
 	} else {
-		tree = parents[0].String() + "^{tree}"
+		tree = writeCommitConfig.parents[0].String() + "^{tree}"
 	}
 
 	if writeCommitConfig.authorName == "" {
-		writeCommitConfig.authorName = committerName
+		writeCommitConfig.authorName = DefaultCommitterName
 	}
 
 	if writeCommitConfig.authorDate.IsZero() {
@@ -164,7 +169,7 @@ func WriteCommit(t testing.TB, cfg config.Cfg, repoPath string, opts ...WriteCom
 	}
 
 	if writeCommitConfig.committerName == "" {
-		writeCommitConfig.committerName = committerName
+		writeCommitConfig.committerName = DefaultCommitterName
 	}
 
 	if writeCommitConfig.committerDate.IsZero() {
@@ -176,7 +181,7 @@ func WriteCommit(t testing.TB, cfg config.Cfg, repoPath string, opts ...WriteCom
 	// --allow-empty".
 	commitArgs := []string{
 		"-c", fmt.Sprintf("user.name=%s", writeCommitConfig.committerName),
-		"-c", fmt.Sprintf("user.email=%s", committerEmail),
+		"-c", fmt.Sprintf("user.email=%s", DefaultCommitterMail),
 		"-C", repoPath,
 		"commit-tree", "-F", "-", tree,
 	}
@@ -196,13 +201,13 @@ func WriteCommit(t testing.TB, cfg config.Cfg, repoPath string, opts ...WriteCom
 	env = append(env,
 		fmt.Sprintf("GIT_AUTHOR_DATE=%d %s", writeCommitConfig.authorDate.Unix(), writeCommitConfig.authorDate.Format("-0700")),
 		fmt.Sprintf("GIT_AUTHOR_NAME=%s", writeCommitConfig.authorName),
-		fmt.Sprintf("GIT_AUTHOR_EMAIL=%s", committerEmail),
+		fmt.Sprintf("GIT_AUTHOR_EMAIL=%s", DefaultCommitterMail),
 		fmt.Sprintf("GIT_COMMITTER_DATE=%d %s", writeCommitConfig.committerDate.Unix(), writeCommitConfig.committerDate.Format("-0700")),
 		fmt.Sprintf("GIT_COMMITTER_NAME=%s", writeCommitConfig.committerName),
-		fmt.Sprintf("GIT_COMMITTER_EMAIL=%s", committerEmail),
+		fmt.Sprintf("GIT_COMMITTER_EMAIL=%s", DefaultCommitterMail),
 	)
 
-	for _, parent := range parents {
+	for _, parent := range writeCommitConfig.parents {
 		commitArgs = append(commitArgs, "-p", parent.String())
 	}
 
diff --git a/internal/git/gittest/commit_test.go b/internal/git/gittest/commit_test.go
index e970079d2..d1f279554 100644
--- a/internal/git/gittest/commit_test.go
+++ b/internal/git/gittest/commit_test.go
@@ -1,5 +1,3 @@
-//go:build !gitaly_test_sha256
-
 package gittest
 
 import (
@@ -15,17 +13,14 @@ import (
 func TestWriteCommit(t *testing.T) {
 	cfg, _, repoPath := setup(t)
 
-	defaultCommitter := "Scrooge McDuck <scrooge@mcduck.com> 1572776879 +0100"
-	defaultParentID := "1a0b36b3cdad1d2ee32457c102a8c0b7056fa863"
+	treeEntryA := TreeEntry{Path: "file", Mode: "100644", Content: "something"}
 
-	revisions := map[git.Revision]git.ObjectID{
-		"refs/heads/master":  "",
-		"refs/heads/master~": "",
-	}
-	for revision := range revisions {
-		oid := Exec(t, cfg, "-C", repoPath, "rev-parse", revision.String())
-		revisions[revision] = git.ObjectID(text.ChompBytes(oid))
-	}
+	treeA := WriteTree(t, cfg, repoPath, []TreeEntry{treeEntryA})
+	treeB := WriteTree(t, cfg, repoPath, []TreeEntry{
+		{Path: "file", Mode: "100644", Content: "changed"},
+	})
+	commitA := WriteCommit(t, cfg, repoPath, WithTree(treeA))
+	commitB := WriteCommit(t, cfg, repoPath, WithTree(treeB))
 
 	for _, tc := range []struct {
 		desc                string
@@ -37,10 +32,9 @@ func TestWriteCommit(t *testing.T) {
 		{
 			desc: "no options",
 			expectedCommit: strings.Join([]string{
-				"tree 91639b9835ff541f312fd2735f639a50bf35d472",
-				"parent " + defaultParentID,
-				"author " + defaultCommitter,
-				"committer " + defaultCommitter,
+				"tree " + DefaultObjectHash.EmptyTreeOID.String(),
+				"author " + DefaultCommitterSignature,
+				"committer " + DefaultCommitterSignature,
 				"",
 				"message",
 			}, "\n"),
@@ -51,10 +45,9 @@ func TestWriteCommit(t *testing.T) {
 				WithMessage("my custom message\n\nfoobar\n"),
 			},
 			expectedCommit: strings.Join([]string{
-				"tree 91639b9835ff541f312fd2735f639a50bf35d472",
-				"parent " + defaultParentID,
-				"author " + defaultCommitter,
-				"committer " + defaultCommitter,
+				"tree " + DefaultObjectHash.EmptyTreeOID.String(),
+				"author " + DefaultCommitterSignature,
+				"committer " + DefaultCommitterSignature,
 				"",
 				"my custom message",
 				"",
@@ -68,10 +61,9 @@ func TestWriteCommit(t *testing.T) {
 				WithAuthorDate(time.Date(2005, 4, 7, 15, 13, 13, 0, time.FixedZone("UTC-7", -7*60*60))),
 			},
 			expectedCommit: strings.Join([]string{
-				"tree 91639b9835ff541f312fd2735f639a50bf35d472",
-				"parent " + defaultParentID,
+				"tree " + DefaultObjectHash.EmptyTreeOID.String(),
 				"author John Doe <scrooge@mcduck.com> 1112911993 -0700",
-				"committer " + defaultCommitter,
+				"committer " + DefaultCommitterSignature,
 				"",
 				"message",
 			}, "\n"),
@@ -83,9 +75,8 @@ func TestWriteCommit(t *testing.T) {
 				WithCommitterDate(time.Date(2005, 4, 7, 15, 13, 13, 0, time.FixedZone("UTC-7", -7*60*60))),
 			},
 			expectedCommit: strings.Join([]string{
-				"tree 91639b9835ff541f312fd2735f639a50bf35d472",
-				"parent " + defaultParentID,
-				"author Scrooge McDuck <scrooge@mcduck.com> 1572776879 +0100",
+				"tree " + DefaultObjectHash.EmptyTreeOID.String(),
+				"author " + DefaultCommitterSignature,
 				"committer John Doe <scrooge@mcduck.com> 1112911993 -0700",
 				"",
 				"message",
@@ -97,9 +88,9 @@ func TestWriteCommit(t *testing.T) {
 				WithParents(),
 			},
 			expectedCommit: strings.Join([]string{
-				"tree 4b825dc642cb6eb9a060e54bf8d69288fbee4904",
-				"author " + defaultCommitter,
-				"committer " + defaultCommitter,
+				"tree " + DefaultObjectHash.EmptyTreeOID.String(),
+				"author " + DefaultCommitterSignature,
+				"committer " + DefaultCommitterSignature,
 				"",
 				"message",
 			}, "\n"),
@@ -107,14 +98,14 @@ func TestWriteCommit(t *testing.T) {
 		{
 			desc: "with multiple parents",
 			opts: []WriteCommitOption{
-				WithParents(revisions["refs/heads/master"], revisions["refs/heads/master~"]),
+				WithParents(commitA, commitB),
 			},
 			expectedCommit: strings.Join([]string{
-				"tree 07f8147e8e73aab6c935c296e8cdc5194dee729b",
-				"parent 1e292f8fedd741b75372e19097c76d327140c312",
-				"parent 7975be0116940bf2ad4321f79d02a55c5f7779aa",
-				"author " + defaultCommitter,
-				"committer " + defaultCommitter,
+				"tree " + treeA.String(),
+				"parent " + commitA.String(),
+				"parent " + commitB.String(),
+				"author " + DefaultCommitterSignature,
+				"committer " + DefaultCommitterSignature,
 				"",
 				"message",
 			}, "\n"),
@@ -125,10 +116,9 @@ func TestWriteCommit(t *testing.T) {
 				WithBranch("foo"),
 			},
 			expectedCommit: strings.Join([]string{
-				"tree 91639b9835ff541f312fd2735f639a50bf35d472",
-				"parent " + defaultParentID,
-				"author " + defaultCommitter,
-				"committer " + defaultCommitter,
+				"tree " + DefaultObjectHash.EmptyTreeOID.String(),
+				"author " + DefaultCommitterSignature,
+				"committer " + DefaultCommitterSignature,
 				"",
 				"message",
 			}, "\n"),
@@ -137,44 +127,26 @@ func TestWriteCommit(t *testing.T) {
 		{
 			desc: "with tree entry",
 			opts: []WriteCommitOption{
-				WithTreeEntries(TreeEntry{
-					Content: "foobar",
-					Mode:    "100644",
-					Path:    "file",
-				}),
+				WithTreeEntries(treeEntryA),
 			},
 			expectedCommit: strings.Join([]string{
-				"tree 0a2fde9f84d2642adbfdf7c37560005e2532fd31",
-				"parent " + defaultParentID,
-				"author " + defaultCommitter,
-				"committer " + defaultCommitter,
+				"tree " + treeA.String(),
+				"author " + DefaultCommitterSignature,
+				"committer " + DefaultCommitterSignature,
 				"",
 				"message",
 			}, "\n"),
-			expectedTreeEntries: []TreeEntry{
-				{
-					Content: "foobar",
-					Mode:    "100644",
-					Path:    "file",
-				},
-			},
+			expectedTreeEntries: []TreeEntry{treeEntryA},
 		},
 		{
 			desc: "with tree",
 			opts: []WriteCommitOption{
-				WithTree(WriteTree(t, cfg, repoPath, []TreeEntry{
-					{
-						Content: "something",
-						Mode:    "100644",
-						Path:    "file",
-					},
-				})),
+				WithTree(treeA),
 			},
 			expectedCommit: strings.Join([]string{
-				"tree 52193934b12dbe23bf1d663802d77a04792a79ac",
-				"parent " + defaultParentID,
-				"author " + defaultCommitter,
-				"committer " + defaultCommitter,
+				"tree " + treeA.String(),
+				"author " + DefaultCommitterSignature,
+				"committer " + DefaultCommitterSignature,
 				"",
 				"message",
 			}, "\n"),
diff --git a/internal/git/gittest/delta_islands.go b/internal/git/gittest/delta_islands.go
index 7909c3049..c582d0813 100644
--- a/internal/git/gittest/delta_islands.go
+++ b/internal/git/gittest/delta_islands.go
@@ -50,7 +50,7 @@ func TestDeltaIslands(t *testing.T, cfg config.Cfg, repoPath string, isPoolRepo
 	// chains, and thus neither of the two blobs should use the bad blob as delta base.
 	require.NoError(t, repack(), "repack after delta island setup")
 	require.Equal(t, blob2ID, deltaBase(t, cfg, repoPath, blob1ID), "blob 1 delta base should be blob 2 after repack")
-	require.Equal(t, git.ObjectHashSHA1.ZeroOID.String(), deltaBase(t, cfg, repoPath, blob2ID), "blob 2 should not be delta compressed after repack")
+	require.Equal(t, DefaultObjectHash.ZeroOID.String(), deltaBase(t, cfg, repoPath, blob2ID), "blob 2 should not be delta compressed after repack")
 }
 
 func commitBlob(t *testing.T, cfg config.Cfg, repoPath, ref string, content string) string {
@@ -62,7 +62,6 @@ func commitBlob(t *testing.T, cfg config.Cfg, repoPath, ref string, content stri
 		WithTreeEntries(TreeEntry{
 			Mode: "100644", OID: blobID, Path: "file",
 		}),
-		WithParents(),
 	)
 
 	Exec(t, cfg, "-C", repoPath, "update-ref", ref, commitID.String())
diff --git a/internal/git/gittest/intercepting_command_factory_test.go b/internal/git/gittest/intercepting_command_factory_test.go
index 1dc2070b9..d93f68afc 100644
--- a/internal/git/gittest/intercepting_command_factory_test.go
+++ b/internal/git/gittest/intercepting_command_factory_test.go
@@ -1,5 +1,3 @@
-//go:build !gitaly_test_sha256
-
 package gittest
 
 import (
diff --git a/internal/git/gittest/objects.go b/internal/git/gittest/objects.go
index aafca61b2..0a740326e 100644
--- a/internal/git/gittest/objects.go
+++ b/internal/git/gittest/objects.go
@@ -15,6 +15,11 @@ import (
 	"gitlab.com/gitlab-org/gitaly/v15/internal/helper/text"
 )
 
+// ObjectHashIsSHA256 returns if the current default object hash is SHA256.
+func ObjectHashIsSHA256() bool {
+	return DefaultObjectHash.EmptyTreeOID == git.ObjectHashSHA256.EmptyTreeOID
+}
+
 // RequireObjectExists asserts that the given repository does contain an object with the specified
 // object ID.
 func RequireObjectExists(t testing.TB, cfg config.Cfg, repoPath string, objectID git.ObjectID) {
diff --git a/internal/git/gittest/ref_test.go b/internal/git/gittest/ref_test.go
index 0753ef00f..afbf5c6b1 100644
--- a/internal/git/gittest/ref_test.go
+++ b/internal/git/gittest/ref_test.go
@@ -1,5 +1,3 @@
-//go:build !gitaly_test_sha256
-
 package gittest
 
 import (
@@ -12,8 +10,7 @@ import (
 func TestResolveRevision(t *testing.T) {
 	cfg, _, repoPath := setup(t)
 
-	require.Equal(t,
-		git.ObjectID("1e292f8fedd741b75372e19097c76d327140c312"),
-		ResolveRevision(t, cfg, repoPath, "refs/heads/master"),
-	)
+	commitID := WriteCommit(t, cfg, repoPath, WithBranch(git.DefaultBranch))
+
+	require.Equal(t, commitID, ResolveRevision(t, cfg, repoPath, git.DefaultBranch))
 }
diff --git a/internal/git/gittest/repo.go b/internal/git/gittest/repo.go
index 1b4b08bb3..201f459b1 100644
--- a/internal/git/gittest/repo.go
+++ b/internal/git/gittest/repo.go
@@ -144,6 +144,10 @@ func CreateRepository(ctx context.Context, t testing.TB, cfg config.Cfg, configs
 	}
 
 	if opts.Seed != "" {
+		if ObjectHashIsSHA256() {
+			require.FailNow(t, "seeded repository creation not supported with SHA256")
+		}
+
 		_, err := client.CreateRepositoryFromURL(ctx, &gitalypb.CreateRepositoryFromURLRequest{
 			Repository: repository,
 			Url:        testRepositoryPath(t, opts.Seed),
@@ -290,6 +294,10 @@ type CloneRepoOpts struct {
 // CloneRepo clones a new copy of test repository under a subdirectory in the storage root. You can
 // either pass no or exactly one CloneRepoOpts.
 func CloneRepo(t testing.TB, cfg config.Cfg, storage config.Storage, opts ...CloneRepoOpts) (*gitalypb.Repository, string) {
+	if ObjectHashIsSHA256() {
+		require.FailNow(t, "seeded repository creation not supported with SHA256")
+	}
+
 	require.Less(t, len(opts), 2, "you must either pass no or exactly one option")
 
 	opt := CloneRepoOpts{}
diff --git a/internal/git/gittest/repository_suite.go b/internal/git/gittest/repository_suite.go
index 83db63614..676e17564 100644
--- a/internal/git/gittest/repository_suite.go
+++ b/internal/git/gittest/repository_suite.go
@@ -96,7 +96,7 @@ func testRepositoryHasBranches(t *testing.T, cfg config.Cfg, getRepository GetRe
 
 	repo, repoPath := getRepository(ctx, t, false)
 
-	emptyCommit := text.ChompBytes(Exec(t, cfg, "-C", repoPath, "commit-tree", git.ObjectHashSHA1.EmptyTreeOID.String()))
+	emptyCommit := text.ChompBytes(Exec(t, cfg, "-C", repoPath, "commit-tree", DefaultObjectHash.EmptyTreeOID.String()))
 
 	Exec(t, cfg, "-C", repoPath, "update-ref", "refs/headsbranch", emptyCommit)
 
@@ -124,7 +124,7 @@ func testRepositoryGetDefaultBranch(t *testing.T, cfg config.Cfg, getRepository
 			desc: "default ref",
 			repo: func(t *testing.T) git.Repository {
 				repo, repoPath := getRepository(ctx, t, false)
-				oid := WriteCommit(t, cfg, repoPath, WithParents(), WithBranch("apple"))
+				oid := WriteCommit(t, cfg, repoPath, WithBranch("apple"))
 				WriteCommit(t, cfg, repoPath, WithParents(oid), WithBranch("main"))
 				return repo
 			},
@@ -134,7 +134,7 @@ func testRepositoryGetDefaultBranch(t *testing.T, cfg config.Cfg, getRepository
 			desc: "legacy default ref",
 			repo: func(t *testing.T) git.Repository {
 				repo, repoPath := getRepository(ctx, t, false)
-				oid := WriteCommit(t, cfg, repoPath, WithParents(), WithBranch("apple"))
+				oid := WriteCommit(t, cfg, repoPath, WithBranch("apple"))
 				WriteCommit(t, cfg, repoPath, WithParents(oid), WithBranch("master"))
 				return repo
 			},
@@ -151,7 +151,7 @@ func testRepositoryGetDefaultBranch(t *testing.T, cfg config.Cfg, getRepository
 			desc: "one branch",
 			repo: func(t *testing.T) git.Repository {
 				repo, repoPath := getRepository(ctx, t, false)
-				WriteCommit(t, cfg, repoPath, WithParents(), WithBranch("apple"))
+				WriteCommit(t, cfg, repoPath, WithBranch("apple"))
 				return repo
 			},
 			expectedName: git.NewReferenceNameFromBranchName("apple"),
@@ -160,7 +160,7 @@ func testRepositoryGetDefaultBranch(t *testing.T, cfg config.Cfg, getRepository
 			desc: "no default branches",
 			repo: func(t *testing.T) git.Repository {
 				repo, repoPath := getRepository(ctx, t, false)
-				oid := WriteCommit(t, cfg, repoPath, WithParents(), WithBranch("apple"))
+				oid := WriteCommit(t, cfg, repoPath, WithBranch("apple"))
 				WriteCommit(t, cfg, repoPath, WithParents(oid), WithBranch("banana"))
 				return repo
 			},
diff --git a/internal/git/gittest/tag.go b/internal/git/gittest/tag.go
index 09cfa2f5d..047d952b3 100644
--- a/internal/git/gittest/tag.go
+++ b/internal/git/gittest/tag.go
@@ -39,13 +39,10 @@ func WriteTag(
 		config = optionalConfig[0]
 	}
 
-	committerName := "Scrooge McDuck"
-	committerEmail := "scrooge@mcduck.com"
-
 	args := []string{
 		"-C", repoPath,
-		"-c", fmt.Sprintf("user.name=%s", committerName),
-		"-c", fmt.Sprintf("user.email=%s", committerEmail),
+		"-c", fmt.Sprintf("user.name=%s", DefaultCommitterName),
+		"-c", fmt.Sprintf("user.email=%s", DefaultCommitterMail),
 		"tag",
 	}
 
diff --git a/internal/git/gittest/testhelper_test.go b/internal/git/gittest/testhelper_test.go
index 42e7bf48c..dd24561fa 100644
--- a/internal/git/gittest/testhelper_test.go
+++ b/internal/git/gittest/testhelper_test.go
@@ -1,5 +1,3 @@
-//go:build !gitaly_test_sha256
-
 package gittest
 
 import (
@@ -54,7 +52,7 @@ func setup(t testing.TB) (config.Cfg, *gitalypb.Repository, string) {
 
 	require.NoError(t, cfg.Validate())
 
-	repo, repoPath := CloneRepo(t, cfg, cfg.Storages[0])
+	repo, repoPath := InitRepo(t, cfg, cfg.Storages[0])
 
 	return cfg, repo, repoPath
 }
diff --git a/internal/git/gittest/tree.go b/internal/git/gittest/tree.go
index 7b93c996f..41194ed72 100644
--- a/internal/git/gittest/tree.go
+++ b/internal/git/gittest/tree.go
@@ -2,7 +2,6 @@ package gittest
 
 import (
 	"bytes"
-	"crypto/sha1"
 	"encoding/hex"
 	"fmt"
 	"testing"
@@ -36,8 +35,12 @@ func RequireTree(t testing.TB, cfg config.Cfg, repoPath, treeish string, expecte
 		}
 
 		blob := fmt.Sprintf("blob %d\000%s", len(entry.Content), entry.Content)
-		hash := sha1.Sum([]byte(blob))
-		expectedEntries[i].OID = git.ObjectID(hex.EncodeToString(hash[:]))
+
+		hasher := DefaultObjectHash.Hash()
+		_, err := hasher.Write([]byte(blob))
+		require.NoError(t, err)
+
+		expectedEntries[i].OID = git.ObjectID(hex.EncodeToString(hasher.Sum(nil)))
 	}
 
 	var actualEntries []TreeEntry
diff --git a/internal/git/gittest/tree_test.go b/internal/git/gittest/tree_test.go
index 09ce729d7..c136857c6 100644
--- a/internal/git/gittest/tree_test.go
+++ b/internal/git/gittest/tree_test.go
@@ -1,18 +1,16 @@
-//go:build !gitaly_test_sha256
-
 package gittest
 
 import (
 	"strings"
 	"testing"
 
-	"github.com/stretchr/testify/require"
 	"gitlab.com/gitlab-org/gitaly/v15/internal/git"
 )
 
 func TestWriteTree(t *testing.T) {
 	cfg, _, repoPath := setup(t)
 
+	differentContentBlobID := WriteBlob(t, cfg, repoPath, []byte("different content"))
 	blobID := WriteBlob(t, cfg, repoPath, []byte("foobar\n"))
 	treeID := WriteTree(t, cfg, repoPath, []TreeEntry{
 		{
@@ -26,7 +24,6 @@ func TestWriteTree(t *testing.T) {
 		desc            string
 		entries         []TreeEntry
 		expectedEntries []TreeEntry
-		expectedOID     git.ObjectID
 	}{
 		{
 			desc: "entry with blob OID",
@@ -45,7 +42,6 @@ func TestWriteTree(t *testing.T) {
 					Path:    "file",
 				},
 			},
-			expectedOID: "54a22f36d78d0ba7964f71ff72c7309edecab857",
 		},
 		{
 			desc: "entry with blob content",
@@ -58,13 +54,12 @@ func TestWriteTree(t *testing.T) {
 			},
 			expectedEntries: []TreeEntry{
 				{
-					OID:     "323fae03f4606ea9991df8befbb2fca795e648fa",
+					OID:     blobID,
 					Content: "foobar\n",
 					Mode:    "100644",
 					Path:    "file",
 				},
 			},
-			expectedOID: "54a22f36d78d0ba7964f71ff72c7309edecab857",
 		},
 		{
 			desc: "entry with tree OID",
@@ -83,7 +78,6 @@ func TestWriteTree(t *testing.T) {
 					Path:    "dir/file",
 				},
 			},
-			expectedOID: "c69f8fc9c97fcae2a80ba1578c493171984d810a",
 		},
 		{
 			desc: "mixed tree and blob entries",
@@ -118,29 +112,27 @@ func TestWriteTree(t *testing.T) {
 					Path:    "file1",
 				},
 				{
-					OID:     "9b62abfb7f69b6d5801a232a9e6c332a10c9cafc",
+					OID:     differentContentBlobID,
 					Content: "different content",
 					Mode:    "100644",
 					Path:    "file2",
 				},
 			},
-			expectedOID: "70a96b29b67eb29344f399c1c4bc0047568e8dba",
 		},
 		{
 			desc: "two entries with nonexistant objects",
 			entries: []TreeEntry{
 				{
-					OID:  git.ObjectID(strings.Repeat("1", 40)),
+					OID:  git.ObjectID(strings.Repeat("1", DefaultObjectHash.Hash().Size()*2)),
 					Mode: "100644",
 					Path: "file",
 				},
 				{
-					OID:  git.ObjectID(strings.Repeat("0", 40)),
+					OID:  DefaultObjectHash.ZeroOID,
 					Mode: "100644",
 					Path: "file",
 				},
 			},
-			expectedOID: "09e7f53dec572807e651fc368d834f9744a5a42c",
 		},
 	} {
 		t.Run(tc.desc, func(t *testing.T) {
@@ -149,8 +141,6 @@ func TestWriteTree(t *testing.T) {
 			if tc.expectedEntries != nil {
 				RequireTree(t, cfg, repoPath, oid.String(), tc.expectedEntries)
 			}
-
-			require.Equal(t, tc.expectedOID, oid)
 		})
 	}
 }
diff --git a/internal/git/housekeeping/objects_test.go b/internal/git/housekeeping/objects_test.go
index 7d56e1d4b..6156c65bf 100644
--- a/internal/git/housekeeping/objects_test.go
+++ b/internal/git/housekeeping/objects_test.go
@@ -40,7 +40,7 @@ func TestRepackObjects(t *testing.T) {
 		repoProto, repoPath := gittest.InitRepo(t, cfg, cfg.Storages[0])
 		repo := localrepo.NewTestRepo(t, cfg, repoProto)
 
-		gittest.WriteCommit(t, cfg, repoPath, gittest.WithParents(), gittest.WithBranch("main"))
+		gittest.WriteCommit(t, cfg, repoPath, gittest.WithBranch("main"))
 
 		requireObjectCount(t, repoPath, 1)
 		requirePackfileCount(t, repoPath, 0)
diff --git a/internal/git/housekeeping/optimize_repository_test.go b/internal/git/housekeeping/optimize_repository_test.go
index c99125018..886765b5a 100644
--- a/internal/git/housekeeping/optimize_repository_test.go
+++ b/internal/git/housekeeping/optimize_repository_test.go
@@ -385,7 +385,7 @@ func TestPackRefsIfNeeded(t *testing.T) {
 			repo := localrepo.NewTestRepo(t, cfg, repoProto)
 
 			// Write an empty commit such that we can create valid refs.
-			commitID := gittest.WriteCommit(t, cfg, repoPath, gittest.WithParents())
+			commitID := gittest.WriteCommit(t, cfg, repoPath)
 			looseRefContent := []byte(commitID.String() + "\n")
 
 			// We first create a single big packfile which is used to determine the
@@ -685,7 +685,7 @@ gitaly_housekeeping_tasks_total{housekeeping_task="total", status="success"} 1
 				})
 
 				for i := 0; i < 16; i++ {
-					gittest.WriteCommit(t, cfg, repoPath, gittest.WithParents(), gittest.WithBranch(fmt.Sprintf("branch-%d", i)))
+					gittest.WriteCommit(t, cfg, repoPath, gittest.WithBranch(fmt.Sprintf("branch-%d", i)))
 				}
 
 				gittest.Exec(t, cfg, "-C", repoPath, "repack", "-A", "--write-bitmap-index")
@@ -1008,7 +1008,7 @@ func TestWriteCommitGraphIfNeeded(t *testing.T) {
 			desc: "repository without commit-graph",
 			setup: func(t *testing.T) (*gitalypb.Repository, string) {
 				repoProto, repoPath := gittest.InitRepo(t, cfg, cfg.Storages[0])
-				gittest.WriteCommit(t, cfg, repoPath, gittest.WithParents(), gittest.WithBranch("main"))
+				gittest.WriteCommit(t, cfg, repoPath, gittest.WithBranch("main"))
 				return repoProto, repoPath
 			},
 			expectedWrite: true,
@@ -1021,7 +1021,7 @@ func TestWriteCommitGraphIfNeeded(t *testing.T) {
 			desc: "repository with old-style unsplit commit-graph",
 			setup: func(t *testing.T) (*gitalypb.Repository, string) {
 				repoProto, repoPath := gittest.InitRepo(t, cfg, cfg.Storages[0])
-				gittest.WriteCommit(t, cfg, repoPath, gittest.WithParents(), gittest.WithBranch("main"))
+				gittest.WriteCommit(t, cfg, repoPath, gittest.WithBranch("main"))
 
 				// Write a non-split commit-graph with bloom filters. We should
 				// always rewrite the commit-graphs when we're not using a split
@@ -1043,7 +1043,7 @@ func TestWriteCommitGraphIfNeeded(t *testing.T) {
 			desc: "repository with split commit-graph without bitmap",
 			setup: func(t *testing.T) (*gitalypb.Repository, string) {
 				repoProto, repoPath := gittest.InitRepo(t, cfg, cfg.Storages[0])
-				gittest.WriteCommit(t, cfg, repoPath, gittest.WithParents(), gittest.WithBranch("main"))
+				gittest.WriteCommit(t, cfg, repoPath, gittest.WithBranch("main"))
 
 				// Generate a split commit-graph, but don't enable computation of
 				// changed paths. This should trigger a rewrite so that we can
@@ -1062,7 +1062,7 @@ func TestWriteCommitGraphIfNeeded(t *testing.T) {
 			desc: "repository with split commit-graph with bitmap without repack",
 			setup: func(t *testing.T) (*gitalypb.Repository, string) {
 				repoProto, repoPath := gittest.InitRepo(t, cfg, cfg.Storages[0])
-				gittest.WriteCommit(t, cfg, repoPath, gittest.WithParents(), gittest.WithBranch("main"))
+				gittest.WriteCommit(t, cfg, repoPath, gittest.WithBranch("main"))
 
 				// Write a split commit-graph with bitmaps. This is the state we
 				// want to be in.
@@ -1081,7 +1081,7 @@ func TestWriteCommitGraphIfNeeded(t *testing.T) {
 			desc: "repository with split commit-graph with bitmap with repack",
 			setup: func(t *testing.T) (*gitalypb.Repository, string) {
 				repoProto, repoPath := gittest.InitRepo(t, cfg, cfg.Storages[0])
-				gittest.WriteCommit(t, cfg, repoPath, gittest.WithParents(), gittest.WithBranch("main"))
+				gittest.WriteCommit(t, cfg, repoPath, gittest.WithBranch("main"))
 
 				// Write a split commit-graph with bitmaps. This is the state we
 				// want to be in, so there is no write required if we didn't also
@@ -1101,7 +1101,7 @@ func TestWriteCommitGraphIfNeeded(t *testing.T) {
 			desc: "repository with split commit-graph with bitmap with pruned objects",
 			setup: func(t *testing.T) (*gitalypb.Repository, string) {
 				repoProto, repoPath := gittest.InitRepo(t, cfg, cfg.Storages[0])
-				gittest.WriteCommit(t, cfg, repoPath, gittest.WithParents(), gittest.WithBranch("main"))
+				gittest.WriteCommit(t, cfg, repoPath, gittest.WithBranch("main"))
 
 				// Write a split commit-graph with bitmaps. This is the state we
 				// want to be in, so there is no write required if we didn't also
@@ -1145,7 +1145,7 @@ func TestWriteCommitGraphIfNeeded(t *testing.T) {
 		repo := localrepo.NewTestRepo(t, cfg, repoProto)
 
 		// Write a first commit-graph that contains the root commit, only.
-		rootCommitID := gittest.WriteCommit(t, cfg, repoPath, gittest.WithParents(), gittest.WithBranch("main"))
+		rootCommitID := gittest.WriteCommit(t, cfg, repoPath, gittest.WithBranch("main"))
 		gittest.Exec(t, cfg, "-C", repoPath, "commit-graph", "write", "--reachable", "--split", "--changed-paths")
 
 		// Write a second, incremental commit-graph that contains a commit we're about to
diff --git a/internal/git/localrepo/repo_test.go b/internal/git/localrepo/repo_test.go
index 7b433083a..8d68dc821 100644
--- a/internal/git/localrepo/repo_test.go
+++ b/internal/git/localrepo/repo_test.go
@@ -84,7 +84,6 @@ func TestSize(t *testing.T) {
 				repoProto, repoPath := gittest.InitRepo(t, cfg, cfg.Storages[0])
 
 				gittest.WriteCommit(t, cfg, repoPath,
-					gittest.WithParents(),
 					gittest.WithTreeEntries(
 						gittest.TreeEntry{Path: "file", Mode: "100644", Content: strings.Repeat("a", 1000)},
 					),
@@ -102,7 +101,6 @@ func TestSize(t *testing.T) {
 				repoProto, repoPath := gittest.InitRepo(t, cfg, cfg.Storages[0])
 
 				gittest.WriteCommit(t, cfg, repoPath,
-					gittest.WithParents(),
 					gittest.WithTreeEntries(
 						gittest.TreeEntry{Path: "file", Mode: "100644", Content: strings.Repeat("a", 1000)},
 					),
@@ -119,7 +117,6 @@ func TestSize(t *testing.T) {
 				repoProto, repoPath := gittest.InitRepo(t, cfg, cfg.Storages[0])
 
 				rootCommitID := gittest.WriteCommit(t, cfg, repoPath,
-					gittest.WithParents(),
 					gittest.WithTreeEntries(
 						gittest.TreeEntry{Path: "file", Mode: "100644", Content: strings.Repeat("a", 1000)},
 					),
@@ -145,7 +142,6 @@ func TestSize(t *testing.T) {
 				repoProto, repoPath := gittest.InitRepo(t, cfg, cfg.Storages[0])
 
 				rootCommitID := gittest.WriteCommit(t, cfg, repoPath,
-					gittest.WithParents(),
 					gittest.WithTreeEntries(
 						gittest.TreeEntry{Path: "file", Mode: "100644", Content: strings.Repeat("a", 1000)},
 					),
@@ -173,7 +169,6 @@ func TestSize(t *testing.T) {
 				repoProto, repoPath := gittest.InitRepo(t, cfg, cfg.Storages[0])
 
 				gittest.WriteCommit(t, cfg, repoPath,
-					gittest.WithParents(),
 					gittest.WithTreeEntries(
 						gittest.TreeEntry{Path: "1kbblob", Mode: "100644", Content: strings.Repeat("a", 1000)},
 					),
@@ -181,7 +176,6 @@ func TestSize(t *testing.T) {
 				)
 
 				gittest.WriteCommit(t, cfg, repoPath,
-					gittest.WithParents(),
 					gittest.WithTreeEntries(
 						gittest.TreeEntry{Path: "1kbblob", Mode: "100644", Content: strings.Repeat("x", 2000)},
 					),
@@ -202,7 +196,6 @@ func TestSize(t *testing.T) {
 				repoProto, repoPath := gittest.InitRepo(t, cfg, cfg.Storages[0])
 
 				gittest.WriteCommit(t, cfg, repoPath,
-					gittest.WithParents(),
 					gittest.WithTreeEntries(
 						gittest.TreeEntry{Path: "1kbblob", Mode: "100644", Content: strings.Repeat("a", 1000)},
 					),
@@ -231,7 +224,6 @@ func TestSize(t *testing.T) {
 
 				for _, path := range []string{repoPath, poolPath} {
 					gittest.WriteCommit(t, cfg, path,
-						gittest.WithParents(),
 						gittest.WithTreeEntries(
 							gittest.TreeEntry{Path: "1kbblob", Mode: "100644", Content: strings.Repeat("a", 1000)},
 						),
@@ -264,7 +256,6 @@ func TestSize(t *testing.T) {
 				// exclude it from our size calculations.
 				for _, path := range []string{repoPath, poolPath} {
 					gittest.WriteCommit(t, cfg, path,
-						gittest.WithParents(),
 						gittest.WithTreeEntries(
 							gittest.TreeEntry{Path: "1kbblob", Mode: "100644", Content: strings.Repeat("a", 1000)},
 						),
@@ -296,7 +287,6 @@ func TestSize(t *testing.T) {
 					// We first write one blob into the repo that is the same
 					// across both repositories.
 					rootCommitID := gittest.WriteCommit(t, cfg, path,
-						gittest.WithParents(),
 						gittest.WithTreeEntries(
 							gittest.TreeEntry{Path: "1kbblob", Mode: "100644", Content: strings.Repeat("a", 1000)},
 						),
diff --git a/internal/git/object_id.go b/internal/git/object_id.go
index 4d6083a12..88db74d44 100644
--- a/internal/git/object_id.go
+++ b/internal/git/object_id.go
@@ -3,12 +3,14 @@ package git
 import (
 	"bytes"
 	"context"
+	"crypto/sha1"
+	"crypto/sha256"
 	"encoding/hex"
 	"errors"
 	"fmt"
+	"hash"
 	"regexp"
 
-	"gitlab.com/gitlab-org/gitaly/v15/internal/command"
 	"gitlab.com/gitlab-org/gitaly/v15/internal/helper/text"
 )
 
@@ -16,6 +18,7 @@ var (
 	// ObjectHashSHA1 is the implementation of an object ID via SHA1.
 	ObjectHashSHA1 = ObjectHash{
 		regexp:       regexp.MustCompile(`\A[0-9a-f]{40}\z`),
+		Hash:         sha1.New,
 		EmptyTreeOID: ObjectID("4b825dc642cb6eb9a060e54bf8d69288fbee4904"),
 		ZeroOID:      ObjectID("0000000000000000000000000000000000000000"),
 	}
@@ -23,6 +26,7 @@ var (
 	// ObjectHashSHA256 is the implementation of an object ID via SHA256.
 	ObjectHashSHA256 = ObjectHash{
 		regexp:       regexp.MustCompile(`\A[0-9a-f]{64}\z`),
+		Hash:         sha256.New,
 		EmptyTreeOID: ObjectID("6ef19b41225c5369f1c104d45d8d85efa9b057b53b14b4b9b939dd74decc5321"),
 		ZeroOID:      ObjectID("0000000000000000000000000000000000000000000000000000000000000000"),
 	}
@@ -35,6 +39,8 @@ var (
 // ObjectHash is a hash-function specific implementation of an object ID.
 type ObjectHash struct {
 	regexp *regexp.Regexp
+	// Hash is the hashing function used to hash objects.
+	Hash func() hash.Hash
 	// EmptyTreeOID is the object ID of the tree object that has no directory entries.
 	EmptyTreeOID ObjectID
 	// ZeroOID is the special value that Git uses to signal a ref or object does not exist
@@ -43,17 +49,15 @@ type ObjectHash struct {
 
 // DetectObjectHash detects the object-hash used by the given repository.
 func DetectObjectHash(ctx context.Context, repoExecutor RepositoryExecutor) (ObjectHash, error) {
-	var stdout bytes.Buffer
+	var stdout, stderr bytes.Buffer
 
 	if err := repoExecutor.ExecAndWait(ctx, SubCmd{
-		Name: "config",
-		Args: []string{"extensions.objectFormat"},
-	}, WithStdout(&stdout)); err != nil {
-		if status, ok := command.ExitStatus(err); ok && status == 1 {
-			return ObjectHashSHA1, nil
-		}
-
-		return ObjectHash{}, fmt.Errorf("reading object format: %w", err)
+		Name: "rev-parse",
+		Flags: []Option{
+			Flag{"--show-object-format"},
+		},
+	}, WithStdout(&stdout), WithStderr(&stderr)); err != nil {
+		return ObjectHash{}, fmt.Errorf("reading object format: %w, stderr: %q", err, stderr.String())
 	}
 
 	objectFormat := text.ChompBytes(stdout.Bytes())
diff --git a/internal/git/object_id_test.go b/internal/git/object_id_test.go
index a6b62ffdc..44ac98a46 100644
--- a/internal/git/object_id_test.go
+++ b/internal/git/object_id_test.go
@@ -53,7 +53,10 @@ func TestDetectObjectHash(t *testing.T) {
 					ObjectFormat: "sha1",
 				})
 
-				// Explicitly set the object format to SHA1.
+				// Explicitly set the object format to SHA1. Note that setting the
+				// object format explicitly requires the repository format version
+				// to be at least `1`.
+				gittest.Exec(t, cfg, "-C", repoPath, "config", "core.repositoryFormatVersion", "1")
 				gittest.Exec(t, cfg, "-C", repoPath, "config", "extensions.objectFormat", "sha1")
 
 				return repo
@@ -77,6 +80,22 @@ func TestDetectObjectHash(t *testing.T) {
 			expectedHash: git.ObjectHashSHA256,
 		},
 		{
+			desc: "invalid repository configuration",
+			setup: func(t *testing.T) *gitalypb.Repository {
+				repo, repoPath := gittest.InitRepo(t, cfg, cfg.Storages[0], gittest.InitRepoOpts{
+					ObjectFormat: "sha1",
+				})
+
+				gittest.Exec(t, cfg, "-C", repoPath, "config", "extensions.objectFormat", "sha1")
+
+				return repo
+			},
+			expectedErr: fmt.Errorf(
+				"reading object format: exit status 128, stderr: %q",
+				"fatal: repo version is 0, but v1-only extension found:\n\tobjectformat\n",
+			),
+		},
+		{
 			desc: "unknown hash",
 			setup: func(t *testing.T) *gitalypb.Repository {
 				repo, repoPath := gittest.InitRepo(t, cfg, cfg.Storages[0])
@@ -86,7 +105,9 @@ func TestDetectObjectHash(t *testing.T) {
 
 				return repo
 			},
-			expectedErr: fmt.Errorf("reading object format: exit status 128"),
+			expectedErr: fmt.Errorf(
+				"reading object format: exit status 128, stderr: \"error: invalid value for 'extensions.objectformat'",
+			),
 		},
 	} {
 		t.Run(tc.desc, func(t *testing.T) {
@@ -95,10 +116,16 @@ func TestDetectObjectHash(t *testing.T) {
 
 			hash, err := git.DetectObjectHash(ctx, repo)
 			if tc.expectedErr != nil {
-				require.EqualError(t, err, tc.expectedErr.Error())
+				require.Error(t, err)
+				require.Contains(t, err.Error(), tc.expectedErr.Error())
 			} else {
 				require.NoError(t, err)
 			}
+
+			// Function pointers cannot be compared, so we need to unset them.
+			hash.Hash = nil
+			tc.expectedHash.Hash = nil
+
 			require.Equal(t, tc.expectedHash, hash)
 		})
 	}
diff --git a/internal/git/objectpool/fetch_test.go b/internal/git/objectpool/fetch_test.go
index 880fa2dd3..bb7b5c921 100644
--- a/internal/git/objectpool/fetch_test.go
+++ b/internal/git/objectpool/fetch_test.go
@@ -223,7 +223,6 @@ func testFetchFromOriginRefUpdates(t *testing.T, ctx context.Context) {
 	// it's easy enough to do, so it doesn't hurt.
 	for i := 0; i < 32; i++ {
 		newRefs[fmt.Sprintf("heads/branch-%d", i)] = gittest.WriteCommit(t, cfg, repoPath,
-			gittest.WithParents(),
 			gittest.WithMessage(strconv.Itoa(i)),
 		).String()
 	}
@@ -259,7 +258,7 @@ func testFetchFromOriginRefs(t *testing.T, ctx context.Context) {
 	repoProto, repoPath := gittest.InitRepo(t, cfg, cfg.Storages[0])
 	repo := localrepo.NewTestRepo(t, cfg, repoProto)
 
-	commitID := gittest.WriteCommit(t, cfg, repoPath, gittest.WithParents(), gittest.WithTreeEntries())
+	commitID := gittest.WriteCommit(t, cfg, repoPath, gittest.WithTreeEntries())
 	for _, ref := range []string{"refs/heads/master", "refs/environments/1", "refs/tags/lightweight-tag"} {
 		gittest.Exec(t, cfg, "-C", repoPath, "update-ref", ref, commitID.String())
 	}
diff --git a/internal/git/stats/profile_test.go b/internal/git/stats/profile_test.go
index 5a2b5bd1f..0b6b3030c 100644
--- a/internal/git/stats/profile_test.go
+++ b/internal/git/stats/profile_test.go
@@ -51,7 +51,6 @@ func TestRepositoryProfile(t *testing.T) {
 			gittest.WithTreeEntries(gittest.TreeEntry{
 				Mode: "100644", Path: "blob", OID: git.ObjectID(blobID),
 			}),
-			gittest.WithParents(),
 		)
 		gittest.Exec(t, cfg, "-C", testRepoPath, "update-ref", "refs/heads/"+blobID, commitID.String())
 	}
diff --git a/internal/git/helper_test.go b/internal/git/testhelper_test.go
index 21a27883e..21a27883e 100644
--- a/internal/git/helper_test.go
+++ b/internal/git/testhelper_test.go
diff --git a/internal/gitaly/linguist/linguist_test.go b/internal/gitaly/linguist/linguist_test.go
index c5427bb6a..82eb7bb95 100644
--- a/internal/gitaly/linguist/linguist_test.go
+++ b/internal/gitaly/linguist/linguist_test.go
@@ -164,7 +164,7 @@ func testInstanceStats(t *testing.T, ctx context.Context) {
 				repoProto, repoPath := gittest.InitRepo(t, cfg, cfg.Storages[0])
 				repo := localrepo.NewTestRepo(t, cfg, repoProto)
 
-				oldCommitID := gittest.WriteCommit(t, cfg, repoPath, gittest.WithParents(), gittest.WithTreeEntries(
+				oldCommitID := gittest.WriteCommit(t, cfg, repoPath, gittest.WithTreeEntries(
 					gittest.TreeEntry{Path: "main.rb", Content: "require 'fileutils'", Mode: "100644"},
 				))
 				newCommitID := gittest.WriteCommit(t, cfg, repoPath, gittest.WithParents(oldCommitID), gittest.WithTreeEntries(
diff --git a/internal/gitaly/service/commit/check_objects_exist_test.go b/internal/gitaly/service/commit/check_objects_exist_test.go
index 5873ca776..9628bba02 100644
--- a/internal/gitaly/service/commit/check_objects_exist_test.go
+++ b/internal/gitaly/service/commit/check_objects_exist_test.go
@@ -23,7 +23,7 @@ func TestCheckObjectsExist(t *testing.T) {
 	repo, repoPath := gittest.CreateRepository(ctx, t, cfg)
 
 	commitID1 := gittest.WriteCommit(t, cfg, repoPath,
-		gittest.WithBranch("master"), gittest.WithMessage("commit-1"), gittest.WithParents(),
+		gittest.WithBranch("master"), gittest.WithMessage("commit-1"),
 	)
 	commitID2 := gittest.WriteCommit(t, cfg, repoPath,
 		gittest.WithBranch("feature"), gittest.WithMessage("commit-2"), gittest.WithParents(commitID1),
diff --git a/internal/gitaly/service/commit/find_commit_test.go b/internal/gitaly/service/commit/find_commit_test.go
index e1b9fcd23..42470db91 100644
--- a/internal/gitaly/service/commit/find_commit_test.go
+++ b/internal/gitaly/service/commit/find_commit_test.go
@@ -203,14 +203,14 @@ func TestSuccessfulFindCommitRequest(t *testing.T) {
 				Id:      bigCommitID.String(),
 				Subject: []byte("An empty commit with REALLY BIG message"),
 				Author: &gitalypb.CommitAuthor{
-					Name:     []byte("Scrooge McDuck"),
-					Email:    []byte("scrooge@mcduck.com"),
+					Name:     []byte(gittest.DefaultCommitterName),
+					Email:    []byte(gittest.DefaultCommitterMail),
 					Date:     &timestamppb.Timestamp{Seconds: bigCommit.Author.Date.Seconds},
 					Timezone: []byte("+0100"),
 				},
 				Committer: &gitalypb.CommitAuthor{
-					Name:     []byte("Scrooge McDuck"),
-					Email:    []byte("scrooge@mcduck.com"),
+					Name:     []byte(gittest.DefaultCommitterName),
+					Email:    []byte(gittest.DefaultCommitterMail),
 					Date:     &timestamppb.Timestamp{Seconds: bigCommit.Committer.Date.Seconds},
 					Timezone: []byte("+0100"),
 				},
diff --git a/internal/gitaly/service/commit/list_all_commits_test.go b/internal/gitaly/service/commit/list_all_commits_test.go
index 4efa1b383..c0af3db84 100644
--- a/internal/gitaly/service/commit/list_all_commits_test.go
+++ b/internal/gitaly/service/commit/list_all_commits_test.go
@@ -117,7 +117,6 @@ func TestListAllCommits(t *testing.T) {
 		// manually here and write the commit into the quarantine object directory.
 		commitID := gittest.WriteCommit(t, cfg, repoPath,
 			gittest.WithAlternateObjectDirectory(filepath.Join(repoPath, quarantineDir)),
-			gittest.WithParents(),
 		)
 
 		// We now expect only the quarantined commit to be returned.
@@ -133,14 +132,14 @@ func TestListAllCommits(t *testing.T) {
 			BodySize: 7,
 			TreeId:   "4b825dc642cb6eb9a060e54bf8d69288fbee4904",
 			Author: &gitalypb.CommitAuthor{
-				Name:     []byte("Scrooge McDuck"),
-				Email:    []byte("scrooge@mcduck.com"),
+				Name:     []byte(gittest.DefaultCommitterName),
+				Email:    []byte(gittest.DefaultCommitterMail),
 				Date:     &timestamppb.Timestamp{Seconds: 1572776879},
 				Timezone: []byte("+0100"),
 			},
 			Committer: &gitalypb.CommitAuthor{
-				Name:     []byte("Scrooge McDuck"),
-				Email:    []byte("scrooge@mcduck.com"),
+				Name:     []byte(gittest.DefaultCommitterName),
+				Email:    []byte(gittest.DefaultCommitterMail),
 				Date:     &timestamppb.Timestamp{Seconds: 1572776879},
 				Timezone: []byte("+0100"),
 			},
diff --git a/internal/gitaly/service/commit/list_last_commits_for_tree_test.go b/internal/gitaly/service/commit/list_last_commits_for_tree_test.go
index 122af5123..e9d897834 100644
--- a/internal/gitaly/service/commit/list_last_commits_for_tree_test.go
+++ b/internal/gitaly/service/commit/list_last_commits_for_tree_test.go
@@ -358,7 +358,7 @@ func TestSuccessfulListLastCommitsForTreeRequestWithGlobCharacters(t *testing.T)
 		Path: ":wq", Mode: "040000", OID: gittest.WriteTree(t, cfg, repoPath, []gittest.TreeEntry{
 			{Path: "README.md", Mode: "100644", Content: "something"},
 		}),
-	}), gittest.WithParents())
+	}))
 
 	t.Run("with literal pathspecs", func(t *testing.T) {
 		stream, err := client.ListLastCommitsForTree(ctx, &gitalypb.ListLastCommitsForTreeRequest{
diff --git a/internal/gitaly/service/commit/tree_entries_test.go b/internal/gitaly/service/commit/tree_entries_test.go
index af2c64ca2..659c36651 100644
--- a/internal/gitaly/service/commit/tree_entries_test.go
+++ b/internal/gitaly/service/commit/tree_entries_test.go
@@ -25,7 +25,7 @@ func TestGetTreeEntries_curlyBraces(t *testing.T) {
 	ctx := testhelper.Context(t)
 	cfg, repo, repoPath, client := setupCommitServiceWithRepo(ctx, t)
 
-	commitID := gittest.WriteCommit(t, cfg, repoPath, gittest.WithParents(), gittest.WithTreeEntries(gittest.TreeEntry{
+	commitID := gittest.WriteCommit(t, cfg, repoPath, gittest.WithTreeEntries(gittest.TreeEntry{
 		Path: "issue-46261", Mode: "040000", OID: gittest.WriteTree(t, cfg, repoPath, []gittest.TreeEntry{
 			{
 				Path: "folder", Mode: "040000", OID: gittest.WriteTree(t, cfg, repoPath, []gittest.TreeEntry{
@@ -582,7 +582,7 @@ func TestGetTreeEntries_deepFlatpath(t *testing.T) {
 
 		treeID = gittest.WriteTree(t, cfg, repoPath, []gittest.TreeEntry{treeEntry})
 	}
-	commitID := gittest.WriteCommit(t, cfg, repoPath, gittest.WithParents(), gittest.WithTree(treeID))
+	commitID := gittest.WriteCommit(t, cfg, repoPath, gittest.WithTree(treeID))
 
 	// We make a non-recursive request which tries to fetch tree entrie for the tree structure
 	// we have created above. This should return a single entry, which is the directory we're
diff --git a/internal/gitaly/service/conflicts/resolve_conflicts_test.go b/internal/gitaly/service/conflicts/resolve_conflicts_test.go
index 6dfda1eab..a8dddf7aa 100644
--- a/internal/gitaly/service/conflicts/resolve_conflicts_test.go
+++ b/internal/gitaly/service/conflicts/resolve_conflicts_test.go
@@ -825,6 +825,7 @@ func TestResolveConflictsQuarantine(t *testing.T) {
 
 	sourceBlobOID := gittest.WriteBlob(t, cfg, sourceRepoPath, []byte("contents-1\n"))
 	sourceCommitOID := gittest.WriteCommit(t, cfg, sourceRepoPath,
+		gittest.WithParents("1a0b36b3cdad1d2ee32457c102a8c0b7056fa863"),
 		gittest.WithTreeEntries(gittest.TreeEntry{
 			Path: "file.txt", OID: sourceBlobOID, Mode: "100644",
 		}),
@@ -847,6 +848,7 @@ func TestResolveConflictsQuarantine(t *testing.T) {
 	})
 	targetBlobOID := gittest.WriteBlob(t, cfg, targetRepoPath, []byte("contents-2\n"))
 	targetCommitOID := gittest.WriteCommit(t, cfg, targetRepoPath,
+		gittest.WithParents("1a0b36b3cdad1d2ee32457c102a8c0b7056fa863"),
 		gittest.WithTreeEntries(gittest.TreeEntry{
 			Path: "file.txt", OID: targetBlobOID, Mode: "100644",
 		}),
diff --git a/internal/gitaly/service/diff/raw_test.go b/internal/gitaly/service/diff/raw_test.go
index 5183ebfad..9dff35451 100644
--- a/internal/gitaly/service/diff/raw_test.go
+++ b/internal/gitaly/service/diff/raw_test.go
@@ -6,7 +6,6 @@ import (
 	"io"
 	"regexp"
 	"testing"
-	"time"
 
 	"github.com/stretchr/testify/require"
 	"gitlab.com/gitlab-org/gitaly/v15/internal/git/gittest"
@@ -47,9 +46,9 @@ func TestRawDiff_successful(t *testing.T) {
 	require.NoError(t, err)
 
 	signature := git2go.Signature{
-		Name:  "Scrooge McDuck",
-		Email: "scrooge@mcduck.com",
-		When:  time.Unix(12345, 0),
+		Name:  gittest.DefaultCommitterName,
+		Email: gittest.DefaultCommitterMail,
+		When:  gittest.DefaultCommitTime,
 	}
 
 	// Now that we have read the patch in we verify that it indeed round-trips to the same tree
@@ -150,9 +149,9 @@ func TestRawPatch_successful(t *testing.T) {
 	require.NoError(t, err)
 
 	signature := git2go.Signature{
-		Name:  "Scrooge McDuck",
-		Email: "scrooge@mcduck.com",
-		When:  time.Unix(12345, 0),
+		Name:  gittest.DefaultCommitterName,
+		Email: gittest.DefaultCommitterMail,
+		When:  gittest.DefaultCommitTime,
 	}
 
 	// Now that we have read the patch in we verify that it indeed round-trips to the same tree
diff --git a/internal/gitaly/service/operations/branches_test.go b/internal/gitaly/service/operations/branches_test.go
index b3948c5f1..b07fb5060 100644
--- a/internal/gitaly/service/operations/branches_test.go
+++ b/internal/gitaly/service/operations/branches_test.go
@@ -501,7 +501,7 @@ func TestUserDeleteBranch_allowed(t *testing.T) {
 			))
 
 			repo, repoPath := gittest.CreateRepository(ctx, t, cfg)
-			gittest.WriteCommit(t, cfg, repoPath, gittest.WithParents(), gittest.WithBranch("branch"))
+			gittest.WriteCommit(t, cfg, repoPath, gittest.WithBranch("branch"))
 
 			response, err := client.UserDeleteBranch(ctx, &gitalypb.UserDeleteBranchRequest{
 				Repository: repo,
diff --git a/internal/gitaly/service/operations/rebase_test.go b/internal/gitaly/service/operations/rebase_test.go
index a63655401..7bfbf37d6 100644
--- a/internal/gitaly/service/operations/rebase_test.go
+++ b/internal/gitaly/service/operations/rebase_test.go
@@ -97,7 +97,6 @@ func TestUserRebaseConfirmable_skipEmptyCommits(t *testing.T) {
 
 	// This is the base commit from which both "theirs" and "ours" branch from".
 	baseCommit := gittest.WriteCommit(t, cfg, repoPath,
-		gittest.WithParents(),
 		gittest.WithTreeEntries(
 			gittest.TreeEntry{Mode: "100644", Path: "README", Content: "a\nb\nc\nd\ne\nf\n"},
 		),
@@ -175,9 +174,9 @@ func TestUserRebaseConfirmable_skipEmptyCommits(t *testing.T) {
 		ParentIds: []string{theirs.String()},
 		TreeId:    "b68aeb18813d7f2e180f2cc0bccc128511438b29",
 		Author: &gitalypb.CommitAuthor{
-			Name:     []byte("Scrooge McDuck"),
-			Email:    []byte("scrooge@mcduck.com"),
-			Date:     &timestamppb.Timestamp{Seconds: 1572776879},
+			Name:     []byte(gittest.DefaultCommitterName),
+			Email:    []byte(gittest.DefaultCommitterMail),
+			Date:     timestamppb.New(gittest.DefaultCommitTime),
 			Timezone: []byte("+0100"),
 		},
 		Committer: &gitalypb.CommitAuthor{
@@ -626,7 +625,6 @@ func TestUserRebaseConfirmable_deletedFileInLocalRepo(t *testing.T) {
 	var rootCommitID git.ObjectID
 	for _, path := range []string{localRepoPath, remoteRepoPath} {
 		rootCommitID = gittest.WriteCommit(t, cfg, path,
-			gittest.WithParents(),
 			gittest.WithTreeEntries(
 				gittest.TreeEntry{Path: "change-me", Mode: "100644", Content: "unchanged contents"},
 				gittest.TreeEntry{Path: "delete-me", Mode: "100644", Content: "useless stuff"},
@@ -697,7 +695,6 @@ func TestUserRebaseConfirmable_deletedFileInRemoteRepo(t *testing.T) {
 	var rootCommitID git.ObjectID
 	for _, path := range []string{localRepoPath, remoteRepoPath} {
 		rootCommitID = gittest.WriteCommit(t, cfg, path,
-			gittest.WithParents(),
 			gittest.WithTreeEntries(
 				gittest.TreeEntry{Path: "unchanged", Mode: "100644", Content: "unchanged contents"},
 				gittest.TreeEntry{Path: "delete-me", Mode: "100644", Content: "useless stuff"},
diff --git a/internal/gitaly/service/operations/squash_test.go b/internal/gitaly/service/operations/squash_test.go
index ae063e9a4..3a418a6b0 100644
--- a/internal/gitaly/service/operations/squash_test.go
+++ b/internal/gitaly/service/operations/squash_test.go
@@ -328,7 +328,7 @@ func TestUserSquash_renames(t *testing.T) {
 
 	repoProto, repoPath := gittest.CreateRepository(ctx, t, cfg)
 
-	gittest.WriteCommit(t, cfg, repoPath, gittest.WithParents(), gittest.WithBranch("main"))
+	gittest.WriteCommit(t, cfg, repoPath, gittest.WithBranch("main"))
 
 	repo := localrepo.NewTestRepo(t, cfg, repoProto)
 
@@ -336,7 +336,6 @@ func TestUserSquash_renames(t *testing.T) {
 	renamedFilename := "renamed-file.txt"
 
 	rootCommitID := gittest.WriteCommit(t, cfg, repoPath,
-		gittest.WithParents(),
 		gittest.WithTreeEntries(
 			gittest.TreeEntry{Path: originalFilename, Mode: "100644", Content: "This is a test"},
 		),
@@ -422,7 +421,7 @@ func TestUserSquash_emptyCommit(t *testing.T) {
 	// Set up history with two diverging lines of branches, where both sides have implemented
 	// the same changes. During merge, the diff will thus become empty.
 	base := gittest.WriteCommit(t, cfg, repoPath,
-		gittest.WithParents(), gittest.WithTreeEntries(
+		gittest.WithTreeEntries(
 			gittest.TreeEntry{Path: "a", Content: "base", Mode: "100644"},
 		),
 	)
@@ -670,7 +669,7 @@ func TestUserSquash_ancestry(t *testing.T) {
 
 	// We create an empty parent commit and two commits which both branch off from it. As a
 	// result, they are not direct ancestors of each other.
-	parent := gittest.WriteCommit(t, cfg, repoPath, gittest.WithMessage("p"), gittest.WithTreeEntries(), gittest.WithParents())
+	parent := gittest.WriteCommit(t, cfg, repoPath, gittest.WithMessage("p"), gittest.WithTreeEntries())
 	commit1 := gittest.WriteCommit(t, cfg, repoPath, gittest.WithMessage("1"),
 		gittest.WithTreeEntries(gittest.TreeEntry{Path: "a", Mode: "100644", Content: "a-content"}),
 		gittest.WithParents(parent),
@@ -805,7 +804,6 @@ func TestUserSquash_squashingMerge(t *testing.T) {
 
 	base := gittest.WriteCommit(t, cfg, repoPath, gittest.WithMessage("base"),
 		gittest.WithTreeEntries(gittest.TreeEntry{Path: "a", Mode: "100644", Content: "base-content"}),
-		gittest.WithParents(),
 	)
 	ours := gittest.WriteCommit(t, cfg, repoPath, gittest.WithMessage("ours"),
 		gittest.WithTreeEntries(gittest.TreeEntry{Path: "a", Mode: "100644", Content: "ours-content"}),
diff --git a/internal/gitaly/service/ref/find_all_tags_test.go b/internal/gitaly/service/ref/find_all_tags_test.go
index 9025af082..6ae5ec5fe 100644
--- a/internal/gitaly/service/ref/find_all_tags_test.go
+++ b/internal/gitaly/service/ref/find_all_tags_test.go
@@ -98,9 +98,9 @@ func TestFindAllTags_successful(t *testing.T) {
 			Message:      []byte("commit tag with a commit sha as the name"),
 			MessageSize:  40,
 			Tagger: &gitalypb.CommitAuthor{
-				Name:     []byte("Scrooge McDuck"),
-				Email:    []byte("scrooge@mcduck.com"),
-				Date:     &timestamppb.Timestamp{Seconds: 1572776879},
+				Name:     []byte(gittest.DefaultCommitterName),
+				Email:    []byte(gittest.DefaultCommitterMail),
+				Date:     timestamppb.New(gittest.DefaultCommitTime),
 				Timezone: []byte("+0100"),
 			},
 		},
@@ -111,9 +111,9 @@ func TestFindAllTags_successful(t *testing.T) {
 			Message:      []byte("tag of a tag"),
 			MessageSize:  12,
 			Tagger: &gitalypb.CommitAuthor{
-				Name:     []byte("Scrooge McDuck"),
-				Email:    []byte("scrooge@mcduck.com"),
-				Date:     &timestamppb.Timestamp{Seconds: 1572776879},
+				Name:     []byte(gittest.DefaultCommitterName),
+				Email:    []byte(gittest.DefaultCommitterMail),
+				Date:     timestamppb.New(gittest.DefaultCommitTime),
 				Timezone: []byte("+0100"),
 			},
 		},
@@ -164,8 +164,8 @@ func TestFindAllTags_successful(t *testing.T) {
 			Message:      truncatedPGPTagMsg[146:10386], // first 10240 bytes of tag message
 			MessageSize:  11148,
 			Tagger: &gitalypb.CommitAuthor{
-				Name:     []byte("Scrooge McDuck"),
-				Email:    []byte("scrooge@mcduck.com"),
+				Name:     []byte(gittest.DefaultCommitterName),
+				Email:    []byte(gittest.DefaultCommitterMail),
 				Date:     &timestamppb.Timestamp{Seconds: 1393491261},
 				Timezone: []byte("+0100"),
 			},
@@ -177,9 +177,9 @@ func TestFindAllTags_successful(t *testing.T) {
 			Message:     []byte("Blob tag"),
 			MessageSize: 8,
 			Tagger: &gitalypb.CommitAuthor{
-				Name:     []byte("Scrooge McDuck"),
-				Email:    []byte("scrooge@mcduck.com"),
-				Date:     &timestamppb.Timestamp{Seconds: 1572776879},
+				Name:     []byte(gittest.DefaultCommitterName),
+				Email:    []byte(gittest.DefaultCommitterMail),
+				Date:     timestamppb.New(gittest.DefaultCommitTime),
 				Timezone: []byte("+0100"),
 			},
 		},
@@ -209,9 +209,9 @@ func TestFindAllTags_successful(t *testing.T) {
 			MessageSize:  int64(len(bigMessage)),
 			TargetCommit: gitCommit,
 			Tagger: &gitalypb.CommitAuthor{
-				Name:     []byte("Scrooge McDuck"),
-				Email:    []byte("scrooge@mcduck.com"),
-				Date:     &timestamppb.Timestamp{Seconds: 1572776879},
+				Name:     []byte(gittest.DefaultCommitterName),
+				Email:    []byte(gittest.DefaultCommitterMail),
+				Date:     timestamppb.New(gittest.DefaultCommitTime),
 				Timezone: []byte("+0100"),
 			},
 		},
@@ -227,9 +227,7 @@ func TestFindAllTags_simpleNestedTags(t *testing.T) {
 
 	repoProto, repoPath := gittest.CreateRepository(ctx, t, cfg)
 
-	commitID := gittest.WriteCommit(t, cfg, repoPath,
-		gittest.WithParents(),
-	)
+	commitID := gittest.WriteCommit(t, cfg, repoPath)
 
 	tagID := gittest.WriteTag(t, cfg, repoPath, "my/nested/tag", commitID.Revision())
 
@@ -250,15 +248,15 @@ func TestFindAllTags_simpleNestedTags(t *testing.T) {
 					Subject:  []byte("message"),
 					TreeId:   git.ObjectHashSHA1.EmptyTreeOID.String(),
 					Author: &gitalypb.CommitAuthor{
-						Name:     []byte("Scrooge McDuck"),
-						Email:    []byte("scrooge@mcduck.com"),
-						Date:     &timestamppb.Timestamp{Seconds: 1572776879},
+						Name:     []byte(gittest.DefaultCommitterName),
+						Email:    []byte(gittest.DefaultCommitterMail),
+						Date:     timestamppb.New(gittest.DefaultCommitTime),
 						Timezone: []byte("+0100"),
 					},
 					Committer: &gitalypb.CommitAuthor{
-						Name:     []byte("Scrooge McDuck"),
-						Email:    []byte("scrooge@mcduck.com"),
-						Date:     &timestamppb.Timestamp{Seconds: 1572776879},
+						Name:     []byte(gittest.DefaultCommitterName),
+						Email:    []byte(gittest.DefaultCommitterMail),
+						Date:     timestamppb.New(gittest.DefaultCommitTime),
 						Timezone: []byte("+0100"),
 					},
 				},
@@ -279,7 +277,7 @@ func TestFindAllTags_duplicateAnnotatedTags(t *testing.T) {
 	repoProto, repoPath := gittest.CreateRepository(ctx, t, cfg)
 	repo := localrepo.NewTestRepo(t, cfg, repoProto)
 
-	commitID := gittest.WriteCommit(t, cfg, repoPath, gittest.WithParents())
+	commitID := gittest.WriteCommit(t, cfg, repoPath)
 	date := time.Unix(12345, 0)
 	dateOffset := date.Format("-0700")
 
@@ -306,9 +304,9 @@ func TestFindAllTags_duplicateAnnotatedTags(t *testing.T) {
 	}
 
 	commitAuthor := &gitalypb.CommitAuthor{
-		Name:     []byte("Scrooge McDuck"),
-		Email:    []byte("scrooge@mcduck.com"),
-		Date:     &timestamppb.Timestamp{Seconds: 1572776879},
+		Name:     []byte(gittest.DefaultCommitterName),
+		Email:    []byte(gittest.DefaultCommitterMail),
+		Date:     timestamppb.New(gittest.DefaultCommitTime),
 		Timezone: []byte("+0100"),
 	}
 	commit := &gitalypb.GitCommit{
@@ -429,9 +427,9 @@ func TestFindAllTags_nestedTags(t *testing.T) {
 					Message:     []byte(tagMessage),
 					MessageSize: int64(len([]byte(tagMessage))),
 					Tagger: &gitalypb.CommitAuthor{
-						Name:     []byte("Scrooge McDuck"),
-						Email:    []byte("scrooge@mcduck.com"),
-						Date:     &timestamppb.Timestamp{Seconds: 1572776879},
+						Name:     []byte(gittest.DefaultCommitterName),
+						Email:    []byte(gittest.DefaultCommitterMail),
+						Date:     timestamppb.New(gittest.DefaultCommitTime),
 						Timezone: []byte("+0100"),
 					},
 				}
diff --git a/internal/gitaly/service/ref/list_refs_test.go b/internal/gitaly/service/ref/list_refs_test.go
index 813668ae7..dd89caaf0 100644
--- a/internal/gitaly/service/ref/list_refs_test.go
+++ b/internal/gitaly/service/ref/list_refs_test.go
@@ -21,7 +21,7 @@ func TestServer_ListRefs(t *testing.T) {
 
 	repo, repoPath := gittest.CreateRepository(ctx, t, cfg)
 
-	oldCommitID := gittest.WriteCommit(t, cfg, repoPath, gittest.WithParents())
+	oldCommitID := gittest.WriteCommit(t, cfg, repoPath)
 	newCommitID := gittest.WriteCommit(t, cfg, repoPath,
 		gittest.WithParents(oldCommitID),
 		gittest.WithAuthorDate(time.Date(2011, 2, 16, 14, 1, 0, 0, time.FixedZone("UTC+1", +1*60*60))),
diff --git a/internal/gitaly/service/ref/refs_test.go b/internal/gitaly/service/ref/refs_test.go
index b4dd36197..99e4a3d6f 100644
--- a/internal/gitaly/service/ref/refs_test.go
+++ b/internal/gitaly/service/ref/refs_test.go
@@ -912,9 +912,9 @@ func TestSuccessfulFindTagRequest(t *testing.T) {
 			Message:      []byte("commit tag with a commit sha as the name"),
 			MessageSize:  40,
 			Tagger: &gitalypb.CommitAuthor{
-				Name:     []byte("Scrooge McDuck"),
-				Email:    []byte("scrooge@mcduck.com"),
-				Date:     &timestamppb.Timestamp{Seconds: 1572776879},
+				Name:     []byte(gittest.DefaultCommitterName),
+				Email:    []byte(gittest.DefaultCommitterMail),
+				Date:     timestamppb.New(gittest.DefaultCommitTime),
 				Timezone: []byte("+0100"),
 			},
 		},
@@ -925,9 +925,9 @@ func TestSuccessfulFindTagRequest(t *testing.T) {
 			Message:      []byte("tag of a tag"),
 			MessageSize:  12,
 			Tagger: &gitalypb.CommitAuthor{
-				Name:     []byte("Scrooge McDuck"),
-				Email:    []byte("scrooge@mcduck.com"),
-				Date:     &timestamppb.Timestamp{Seconds: 1572776879},
+				Name:     []byte(gittest.DefaultCommitterName),
+				Email:    []byte(gittest.DefaultCommitterMail),
+				Date:     timestamppb.New(gittest.DefaultCommitTime),
 				Timezone: []byte("+0100"),
 			},
 		},
@@ -978,9 +978,9 @@ func TestSuccessfulFindTagRequest(t *testing.T) {
 			Message:     []byte("Blob tag"),
 			MessageSize: 8,
 			Tagger: &gitalypb.CommitAuthor{
-				Name:     []byte("Scrooge McDuck"),
-				Email:    []byte("scrooge@mcduck.com"),
-				Date:     &timestamppb.Timestamp{Seconds: 1572776879},
+				Name:     []byte(gittest.DefaultCommitterName),
+				Email:    []byte(gittest.DefaultCommitterMail),
+				Date:     timestamppb.New(gittest.DefaultCommitTime),
 				Timezone: []byte("+0100"),
 			},
 		},
@@ -1010,9 +1010,9 @@ func TestSuccessfulFindTagRequest(t *testing.T) {
 			MessageSize:  int64(len(bigMessage)),
 			TargetCommit: gitCommit,
 			Tagger: &gitalypb.CommitAuthor{
-				Name:     []byte("Scrooge McDuck"),
-				Email:    []byte("scrooge@mcduck.com"),
-				Date:     &timestamppb.Timestamp{Seconds: 1572776879},
+				Name:     []byte(gittest.DefaultCommitterName),
+				Email:    []byte(gittest.DefaultCommitterMail),
+				Date:     timestamppb.New(gittest.DefaultCommitTime),
 				Timezone: []byte("+0100"),
 			},
 		},
@@ -1104,9 +1104,9 @@ func TestFindTagNestedTag(t *testing.T) {
 				Message:     []byte(tagMessage),
 				MessageSize: int64(len([]byte(tagMessage))),
 				Tagger: &gitalypb.CommitAuthor{
-					Name:     []byte("Scrooge McDuck"),
-					Email:    []byte("scrooge@mcduck.com"),
-					Date:     &timestamppb.Timestamp{Seconds: 1572776879},
+					Name:     []byte(gittest.DefaultCommitterName),
+					Email:    []byte(gittest.DefaultCommitterMail),
+					Date:     timestamppb.New(gittest.DefaultCommitTime),
 					Timezone: []byte("+0100"),
 				},
 			}
diff --git a/internal/gitaly/service/ref/tag_signatures_test.go b/internal/gitaly/service/ref/tag_signatures_test.go
index 6a9986758..35f91762e 100644
--- a/internal/gitaly/service/ref/tag_signatures_test.go
+++ b/internal/gitaly/service/ref/tag_signatures_test.go
@@ -4,6 +4,7 @@ package ref
 
 import (
 	"errors"
+	"fmt"
 	"io"
 	"strings"
 	"testing"
@@ -25,16 +26,16 @@ func TestGetTagSignatures(t *testing.T) {
 	message1 := strings.Repeat("a", helper.MaxCommitOrTagMessageSize) + "\n"
 	signature1 := string(testhelper.MustReadFile(t, "testdata/tag-1e292f8fedd741b75372e19097c76d327140c312-signature"))
 	tag1ID := gittest.WriteTag(t, cfg, repoPath, "big-tag-1", "master", gittest.WriteTagConfig{Message: message1 + signature1})
-	content1 := "object 1e292f8fedd741b75372e19097c76d327140c312\ntype commit\ntag big-tag-1\ntagger Scrooge McDuck <scrooge@mcduck.com> 1572776879 +0100\n\n" + message1
+	content1 := fmt.Sprintf("object 1e292f8fedd741b75372e19097c76d327140c312\ntype commit\ntag big-tag-1\ntagger %s\n\n%s", gittest.DefaultCommitterSignature, message1)
 
 	message2 := strings.Repeat("b", helper.MaxCommitOrTagMessageSize) + "\n"
 	signature2 := string(testhelper.MustReadFile(t, "testdata/tag-7975be0116940bf2ad4321f79d02a55c5f7779aa-signature"))
 	tag2ID := gittest.WriteTag(t, cfg, repoPath, "big-tag-2", "master~", gittest.WriteTagConfig{Message: message2 + signature2})
-	content2 := "object 7975be0116940bf2ad4321f79d02a55c5f7779aa\ntype commit\ntag big-tag-2\ntagger Scrooge McDuck <scrooge@mcduck.com> 1572776879 +0100\n\n" + message2
+	content2 := fmt.Sprintf("object 7975be0116940bf2ad4321f79d02a55c5f7779aa\ntype commit\ntag big-tag-2\ntagger %s\n\n%s", gittest.DefaultCommitterSignature, message2)
 
 	message3 := "tag message\n"
 	tag3ID := gittest.WriteTag(t, cfg, repoPath, "tag-3", "master~~", gittest.WriteTagConfig{Message: message3})
-	content3 := "object 60ecb67744cb56576c30214ff52294f8ce2def98\ntype commit\ntag tag-3\ntagger Scrooge McDuck <scrooge@mcduck.com> 1572776879 +0100\n\n" + message3
+	content3 := fmt.Sprintf("object 60ecb67744cb56576c30214ff52294f8ce2def98\ntype commit\ntag tag-3\ntagger %s\n\n%s", gittest.DefaultCommitterSignature, message3)
 
 	for _, tc := range []struct {
 		desc               string
diff --git a/internal/gitaly/service/repository/create_fork_test.go b/internal/gitaly/service/repository/create_fork_test.go
index 5b1c0cb86..a58ca9b28 100644
--- a/internal/gitaly/service/repository/create_fork_test.go
+++ b/internal/gitaly/service/repository/create_fork_test.go
@@ -117,7 +117,7 @@ func TestCreateFork_refs(t *testing.T) {
 
 	// Prepare the source repository with a bunch of refs and a non-default HEAD ref so we can
 	// assert that the target repo gets created with the correct set of refs.
-	commitID := gittest.WriteCommit(t, cfg, sourceRepoPath, gittest.WithParents())
+	commitID := gittest.WriteCommit(t, cfg, sourceRepoPath)
 	for _, ref := range []string{
 		"refs/environments/something",
 		"refs/heads/something",
diff --git a/internal/gitaly/service/repository/fetch_remote_test.go b/internal/gitaly/service/repository/fetch_remote_test.go
index a8ede341c..939767ed0 100644
--- a/internal/gitaly/service/repository/fetch_remote_test.go
+++ b/internal/gitaly/service/repository/fetch_remote_test.go
@@ -40,7 +40,7 @@ func TestFetchRemote_checkTagsChanged(t *testing.T) {
 
 	_, remoteRepoPath := gittest.CreateRepository(ctx, t, cfg)
 
-	gittest.WriteCommit(t, cfg, remoteRepoPath, gittest.WithParents(), gittest.WithBranch("main"))
+	gittest.WriteCommit(t, cfg, remoteRepoPath, gittest.WithBranch("main"))
 
 	t.Run("check tags without tags", func(t *testing.T) {
 		repoProto, _ := gittest.CreateRepository(ctx, t, cfg)
@@ -814,7 +814,6 @@ func TestFetchRemote_pooledRepository(t *testing.T) {
 			// remote as "have".
 			_, poolRepoPath := gittest.CreateRepository(ctx, t, cfg)
 			poolCommitID := gittest.WriteCommit(t, cfg, poolRepoPath,
-				gittest.WithParents(),
 				gittest.WithBranch("pooled"),
 				gittest.WithTreeEntries(gittest.TreeEntry{Path: "pool", Mode: "100644", Content: "pool contents"}),
 			)
@@ -829,7 +828,6 @@ func TestFetchRemote_pooledRepository(t *testing.T) {
 			// would actually try to fetch objects.
 			_, remoteRepoPath := gittest.CreateRepository(ctx, t, cfg)
 			gittest.WriteCommit(t, cfg, remoteRepoPath,
-				gittest.WithParents(),
 				gittest.WithBranch("remote"),
 				gittest.WithTreeEntries(gittest.TreeEntry{Path: "remote", Mode: "100644", Content: "remote contents"}),
 			)
diff --git a/internal/gitaly/service/repository/gc_test.go b/internal/gitaly/service/repository/gc_test.go
index 05184b5e5..feaeab138 100644
--- a/internal/gitaly/service/repository/gc_test.go
+++ b/internal/gitaly/service/repository/gc_test.go
@@ -552,7 +552,7 @@ func TestGarbageCollect_commitGraphsWithPrunedObjects(t *testing.T) {
 	repoProto, repoPath := gittest.CreateRepository(ctx, t, cfg)
 
 	// Write a first commit-graph that contains the root commit, only.
-	rootCommitID := gittest.WriteCommit(t, cfg, repoPath, gittest.WithParents(), gittest.WithBranch("main"))
+	rootCommitID := gittest.WriteCommit(t, cfg, repoPath, gittest.WithBranch("main"))
 	gittest.Exec(t, cfg, "-C", repoPath, "commit-graph", "write", "--reachable", "--split", "--changed-paths")
 
 	// Write a second, incremental commit-graph that contains a commit we're about to
diff --git a/internal/gitaly/service/repository/license_test.go b/internal/gitaly/service/repository/license_test.go
index 7fe42580b..bd38c746b 100644
--- a/internal/gitaly/service/repository/license_test.go
+++ b/internal/gitaly/service/repository/license_test.go
@@ -84,7 +84,7 @@ SOFTWARE.`,
 					})
 				}
 
-				gittest.WriteCommit(t, cfg, repoPath, gittest.WithBranch("main"), gittest.WithTreeEntries(treeEntries...), gittest.WithParents())
+				gittest.WriteCommit(t, cfg, repoPath, gittest.WithBranch("main"), gittest.WithTreeEntries(treeEntries...))
 
 				if tc.nonExistentRepository {
 					require.NoError(t, os.RemoveAll(repoPath))
diff --git a/internal/gitaly/service/repository/optimize_test.go b/internal/gitaly/service/repository/optimize_test.go
index 92f9bddfe..61a21499c 100644
--- a/internal/gitaly/service/repository/optimize_test.go
+++ b/internal/gitaly/service/repository/optimize_test.go
@@ -106,7 +106,6 @@ func TestOptimizeRepository(t *testing.T) {
 				OID: git.ObjectID(blobID), Mode: "100644", Path: "blob",
 			}),
 			gittest.WithBranch(blobID),
-			gittest.WithParents(),
 		)
 	}
 
diff --git a/internal/gitaly/service/repository/prune_unreachable_objects_test.go b/internal/gitaly/service/repository/prune_unreachable_objects_test.go
index d5ba20e87..29bb18eac 100644
--- a/internal/gitaly/service/repository/prune_unreachable_objects_test.go
+++ b/internal/gitaly/service/repository/prune_unreachable_objects_test.go
@@ -59,7 +59,7 @@ func TestPruneUnreachableObjects(t *testing.T) {
 		repo, repoPath := gittest.CreateRepository(ctx, t, cfg)
 
 		// Create the commit and a branch pointing to it to make it reachable.
-		commitID := gittest.WriteCommit(t, cfg, repoPath, gittest.WithParents(), gittest.WithBranch("branch"))
+		commitID := gittest.WriteCommit(t, cfg, repoPath, gittest.WithBranch("branch"))
 
 		_, err := client.PruneUnreachableObjects(ctx, &gitalypb.PruneUnreachableObjectsRequest{
 			Repository: repo,
@@ -74,7 +74,7 @@ func TestPruneUnreachableObjects(t *testing.T) {
 		repo, repoPath := gittest.CreateRepository(ctx, t, cfg)
 
 		// Create the commit, but don't create a reference pointing to it.
-		commitID := gittest.WriteCommit(t, cfg, repoPath, gittest.WithParents())
+		commitID := gittest.WriteCommit(t, cfg, repoPath)
 		// Set the object time to something that's close to 30 minutes, but gives us enough
 		// room to not cause flakes.
 		setObjectTime(t, repoPath, commitID, time.Now().Add(-28*time.Minute))
@@ -93,7 +93,7 @@ func TestPruneUnreachableObjects(t *testing.T) {
 		repo, repoPath := gittest.CreateRepository(ctx, t, cfg)
 
 		// Create the commit, but don't create a reference pointing to it.
-		commitID := gittest.WriteCommit(t, cfg, repoPath, gittest.WithParents())
+		commitID := gittest.WriteCommit(t, cfg, repoPath)
 		setObjectTime(t, repoPath, commitID, time.Now().Add(-31*time.Minute))
 
 		_, err := client.PruneUnreachableObjects(ctx, &gitalypb.PruneUnreachableObjectsRequest{
@@ -110,13 +110,13 @@ func TestPruneUnreachableObjects(t *testing.T) {
 	t.Run("repository with mixed objects", func(t *testing.T) {
 		repo, repoPath := gittest.CreateRepository(ctx, t, cfg)
 
-		reachableOldCommit := gittest.WriteCommit(t, cfg, repoPath, gittest.WithParents(), gittest.WithMessage("a"), gittest.WithBranch("branch"))
+		reachableOldCommit := gittest.WriteCommit(t, cfg, repoPath, gittest.WithMessage("a"), gittest.WithBranch("branch"))
 		setObjectTime(t, repoPath, reachableOldCommit, time.Now().Add(-31*time.Minute))
 
-		unreachableRecentCommit := gittest.WriteCommit(t, cfg, repoPath, gittest.WithMessage("b"), gittest.WithParents())
+		unreachableRecentCommit := gittest.WriteCommit(t, cfg, repoPath, gittest.WithMessage("b"))
 		setObjectTime(t, repoPath, unreachableRecentCommit, time.Now().Add(-28*time.Minute))
 
-		unreachableOldCommit := gittest.WriteCommit(t, cfg, repoPath, gittest.WithMessage("c"), gittest.WithParents())
+		unreachableOldCommit := gittest.WriteCommit(t, cfg, repoPath, gittest.WithMessage("c"))
 		setObjectTime(t, repoPath, unreachableOldCommit, time.Now().Add(-31*time.Minute))
 
 		_, err := client.PruneUnreachableObjects(ctx, &gitalypb.PruneUnreachableObjectsRequest{
@@ -141,7 +141,7 @@ func TestPruneUnreachableObjects(t *testing.T) {
 		// Write two commits into the repository and create a commit-graph. The second
 		// commit will become unreachable and will be pruned, but will be contained in the
 		// commit-graph.
-		rootCommitID := gittest.WriteCommit(t, cfg, repoPath, gittest.WithParents())
+		rootCommitID := gittest.WriteCommit(t, cfg, repoPath)
 		unreachableCommitID := gittest.WriteCommit(t, cfg, repoPath, gittest.WithParents(rootCommitID), gittest.WithBranch("main"))
 		gittest.Exec(t, cfg, "-C", repoPath, "commit-graph", "write", "--reachable", "--split", "--changed-paths")
 
diff --git a/internal/gitaly/service/repository/rename_test.go b/internal/gitaly/service/repository/rename_test.go
index a394f0798..cf7267308 100644
--- a/internal/gitaly/service/repository/rename_test.go
+++ b/internal/gitaly/service/repository/rename_test.go
@@ -67,7 +67,7 @@ func testRenameRepositoryDestinationExists(t *testing.T, ctx context.Context) {
 	require.NoError(t, err)
 
 	destinationRepoPath := filepath.Join(cfg.Storages[0].Path, gittest.GetReplicaPath(ctx, t, cfg, existingDestinationRepo))
-	commitID := gittest.WriteCommit(t, cfg, destinationRepoPath, gittest.WithParents())
+	commitID := gittest.WriteCommit(t, cfg, destinationRepoPath)
 
 	_, err = client.RenameRepository(ctx, &gitalypb.RenameRepositoryRequest{
 		Repository:   renamedRepo,
diff --git a/internal/gitaly/service/smarthttp/upload_pack_test.go b/internal/gitaly/service/smarthttp/upload_pack_test.go
index 0f3da43dc..02ca6296e 100644
--- a/internal/gitaly/service/smarthttp/upload_pack_test.go
+++ b/internal/gitaly/service/smarthttp/upload_pack_test.go
@@ -139,7 +139,6 @@ func testServerPostUploadPackGitConfigOptions(t *testing.T, ctx context.Context,
 	// the gitconfig indeed is applied because we should not be able to fetch the hidden ref.
 	baseID := gittest.WriteCommit(t, cfg, repoPath,
 		gittest.WithMessage("base commit"),
-		gittest.WithParents(),
 		gittest.WithBranch("main"),
 	)
 	hiddenID := gittest.WriteCommit(t, cfg, repoPath,
diff --git a/internal/gitaly/service/wiki/find_page_test.go b/internal/gitaly/service/wiki/find_page_test.go
index 482337281..b1e59e295 100644
--- a/internal/gitaly/service/wiki/find_page_test.go
+++ b/internal/gitaly/service/wiki/find_page_test.go
@@ -469,7 +469,6 @@ func testSuccessfulWikiFindPageRequestWithTrailers(t *testing.T, cfg config.Cfg,
 
 	gittest.WriteCommit(t, cfg, repoPath,
 		gittest.WithBranch("main"),
-		gittest.WithParents(),
 		gittest.WithMessage("main branch, empty commit"),
 	)