git2go: Add optional Committer to MergeCommand

Squash commits in GitLab use different committer and author.
Committer is the user that merges, and author is the user
that created the MR.
As we want to add squashing to this command, we have to make
sure that we support Committer* arguments as well.

Committer variables are optional, author data is
used when they are empty.
That way this change is backward compatible.
However, if at least one of Committer* variables are set,
all of them have to be.

2 files changed, 52 insertions, 4 deletions

diff --git a/cmd/gitaly-git2go/merge.go b/cmd/gitaly-git2go/merge.go
index 541cecf84..f97125061 100644
--- a/cmd/gitaly-git2go/merge.go
+++ b/cmd/gitaly-git2go/merge.go
@@ -92,8 +92,13 @@ func merge(request git2go.MergeCommand) (string, error) {
 		return "", fmt.Errorf("could not write tree: %w", err)
 	}
 
-	committer := git.Signature(git2go.NewSignature(request.AuthorName, request.AuthorMail, request.AuthorDate))
-	commit, err := repo.CreateCommitFromIds("", &committer, &committer, request.Message, tree, ours.Id(), theirs.Id())
+	author := git.Signature(git2go.NewSignature(request.AuthorName, request.AuthorMail, request.AuthorDate))
+	committer := author
+	if request.CommitterMail != "" {
+		committer = git.Signature(git2go.NewSignature(request.CommitterName, request.CommitterMail, request.CommitterDate))
+	}
+
+	commit, err := repo.CreateCommitFromIds("", &author, &committer, request.Message, tree, ours.Id(), theirs.Id())
 	if err != nil {
 		return "", fmt.Errorf("could not create merge commit: %w", err)
 	}
diff --git a/cmd/gitaly-git2go/merge_test.go b/cmd/gitaly-git2go/merge_test.go
index c63650fc6..b9fff3f6e 100644
--- a/cmd/gitaly-git2go/merge_test.go
+++ b/cmd/gitaly-git2go/merge_test.go
@@ -65,6 +65,22 @@ func TestMerge_missingArguments(t *testing.T) {
 			request:     git2go.MergeCommand{Repository: repoPath, AuthorName: "Foo", AuthorMail: "foo@example.com", Message: "Foo", Ours: "HEAD"},
 			expectedErr: "merge: invalid parameters: missing theirs",
 		},
+		// Committer* arguments are required only when at least one of them is non-empty
+		{
+			desc:        "missing committer mail",
+			request:     git2go.MergeCommand{Repository: repoPath, AuthorName: "Foo", AuthorMail: "foo@example.com", CommitterName: "Bar", Message: "Foo", Theirs: "HEAD", Ours: "HEAD"},
+			expectedErr: "merge: invalid parameters: missing committer mail",
+		},
+		{
+			desc:        "missing committer name",
+			request:     git2go.MergeCommand{Repository: repoPath, AuthorName: "Foo", AuthorMail: "foo@example.com", CommitterMail: "bar@example.com", Message: "Foo", Theirs: "HEAD", Ours: "HEAD"},
+			expectedErr: "merge: invalid parameters: missing committer name",
+		},
+		{
+			desc:        "missing committer date",
+			request:     git2go.MergeCommand{Repository: repoPath, AuthorName: "Foo", AuthorMail: "foo@example.com", CommitterName: "Bar", CommitterMail: "bar@example.com", Message: "Foo", Theirs: "HEAD", Ours: "HEAD"},
+			expectedErr: "merge: invalid parameters: missing committer date",
+		},
 	}
 
 	for _, tc := range testcases {
@@ -101,6 +117,7 @@ func TestMerge_trees(t *testing.T) {
 		ours             map[string]string
 		theirs           map[string]string
 		expected         map[string]string
+		withCommitter    bool
 		expectedResponse git2go.MergeResult
 		expectedErr      error
 	}{
@@ -123,6 +140,25 @@ func TestMerge_trees(t *testing.T) {
 			},
 		},
 		{
+			desc: "trivial merge with different committer succeeds",
+			base: map[string]string{
+				"file": "a",
+			},
+			ours: map[string]string{
+				"file": "a",
+			},
+			theirs: map[string]string{
+				"file": "a",
+			},
+			expected: map[string]string{
+				"file": "a",
+			},
+			withCommitter: true,
+			expectedResponse: git2go.MergeResult{
+				CommitID: "cba8c5ddf5a5a24f2f606e4b62d348feb1214b70",
+			},
+		},
+		{
 			desc: "non-trivial merge succeeds",
 			base: map[string]string{
 				"file": "a\nb\nc\nd\ne\nf\n",
@@ -193,9 +229,10 @@ func TestMerge_trees(t *testing.T) {
 		theirs := cmdtesthelper.BuildCommit(t, repoPath, []*git.Oid{base}, tc.theirs)
 
 		authorDate := time.Date(2020, 7, 30, 7, 45, 50, 0, time.FixedZone("UTC+2", +2*60*60))
+		committerDate := time.Date(2021, 7, 30, 7, 45, 50, 0, time.FixedZone("UTC+2", +2*60*60))
 
 		t.Run(tc.desc, func(t *testing.T) {
-			response, err := executor.Merge(ctx, repoProto, git2go.MergeCommand{
+			mergeCommand := git2go.MergeCommand{
 				Repository: repoPath,
 				AuthorName: "John Doe",
 				AuthorMail: "john.doe@example.com",
@@ -203,7 +240,13 @@ func TestMerge_trees(t *testing.T) {
 				Message:    "Merge message",
 				Ours:       ours.String(),
 				Theirs:     theirs.String(),
-			})
+			}
+			if tc.withCommitter {
+				mergeCommand.CommitterName = "Jane Doe"
+				mergeCommand.CommitterMail = "jane.doe@example.com"
+				mergeCommand.CommitterDate = committerDate
+			}
+			response, err := executor.Merge(ctx, repoProto, mergeCommand)
 
 			if tc.expectedErr != nil {
 				require.Equal(t, tc.expectedErr, err)