gittest: Add commit option to write objects into alternate ODB

We have several tests which write commit objects into the alternate
object database. While some hand-code this, most use the helper function
`CreateCommitInAlternateObjectDirectory()`. This helper requires manual
assemlby of the command and is thus unnecessarily verbose to be used.

Add a new option to the `WriteCommit()` helper which allows callers to
specify an alternate ODB such that it can be used instead of the old
helper.

1 files changed, 34 insertions, 7 deletions

diff --git a/internal/git/gittest/commit.go b/internal/git/gittest/commit.go
index 1e49149d6..b7e83ee8e 100644
--- a/internal/git/gittest/commit.go
+++ b/internal/git/gittest/commit.go
@@ -21,11 +21,12 @@ const (
 )
 
 type writeCommitConfig struct {
-	branch        string
-	parents       []git.ObjectID
-	committerName string
-	message       string
-	treeEntries   []TreeEntry
+	branch             string
+	parents            []git.ObjectID
+	committerName      string
+	message            string
+	treeEntries        []TreeEntry
+	alternateObjectDir string
 }
 
 // WriteCommitOption is an option which can be passed to WriteCommit.
@@ -74,6 +75,15 @@ func WithCommitterName(name string) WriteCommitOption {
 	}
 }
 
+// WithAlternateObjectDirectory will cause the commit to be written into the given alternate object
+// directory. This can either be an absolute path or a relative path. In the latter case the path
+// is considered to be relative to the repository path.
+func WithAlternateObjectDirectory(alternateObjectDir string) WriteCommitOption {
+	return func(cfg *writeCommitConfig) {
+		cfg.alternateObjectDir = alternateObjectDir
+	}
+}
+
 // WriteCommit writes a new commit into the target repository.
 func WriteCommit(t testing.TB, cfg config.Cfg, repoPath string, opts ...WriteCommitOption) git.ObjectID {
 	t.Helper()
@@ -119,16 +129,33 @@ func WriteCommit(t testing.TB, cfg config.Cfg, repoPath string, opts ...WriteCom
 		"commit-tree", "-F", "-", tree,
 	}
 
+	var env []string
+	if writeCommitConfig.alternateObjectDir != "" {
+		require.True(t, filepath.IsAbs(writeCommitConfig.alternateObjectDir),
+			"alternate object directory must be an absolute path")
+		require.NoError(t, os.MkdirAll(writeCommitConfig.alternateObjectDir, 0o755))
+
+		env = append(env,
+			fmt.Sprintf("GIT_OBJECT_DIRECTORY=%s", writeCommitConfig.alternateObjectDir),
+			fmt.Sprintf("GIT_ALTERNATE_OBJECT_DIRECTORIES=%s", filepath.Join(repoPath, "objects")),
+		)
+	}
+
 	for _, parent := range parents {
 		commitArgs = append(commitArgs, "-p", parent.String())
 	}
 
-	stdout := ExecOpts(t, cfg, ExecConfig{Stdin: stdin}, commitArgs...)
+	stdout := ExecOpts(t, cfg, ExecConfig{
+		Stdin: stdin,
+		Env:   env,
+	}, commitArgs...)
 	oid, err := git.NewObjectIDFromHex(text.ChompBytes(stdout))
 	require.NoError(t, err)
 
 	if writeCommitConfig.branch != "" {
-		Exec(t, cfg, "-C", repoPath, "update-ref", "refs/heads/"+writeCommitConfig.branch, oid.String())
+		ExecOpts(t, cfg, ExecConfig{
+			Env: env,
+		}, "-C", repoPath, "update-ref", "refs/heads/"+writeCommitConfig.branch, oid.String())
 	}
 
 	return oid