operations: Allow unrelated histories in UserMergeBranch

UserMergeBranch will receive requests to merge commits with unrelated
histories. This commit allows that in the RPC.

7188fee10 (2023-11-15: operations: Implement merge() using git-merge-tree(1))
modified the `TestUserMergeBranch_conflict` test to add a common
ancestor. This was incorrect, as we should not have modified existing
tests to match the new implementation. This commit restores the original
test before 7188fee10 so the two commits being merged do not share a
common ancestor.

2 files changed, 8 insertions, 23 deletions

diff --git a/internal/gitaly/service/operations/merge.go b/internal/gitaly/service/operations/merge.go
index fe7b6e198..1bcf9f452 100644
--- a/internal/gitaly/service/operations/merge.go
+++ b/internal/gitaly/service/operations/merge.go
@@ -63,7 +63,7 @@ func (s *Server) merge(
 	ours string,
 	theirs string,
 ) (string, error) {
-	treeOID, err := quarantineRepo.MergeTree(ctx, ours, theirs)
+	treeOID, err := quarantineRepo.MergeTree(ctx, ours, theirs, localrepo.WithAllowUnrelatedHistories())
 	if err != nil {
 		return "", err
 	}
diff --git a/internal/gitaly/service/operations/merge_test.go b/internal/gitaly/service/operations/merge_test.go
index 6764a3593..2d44f246d 100644
--- a/internal/gitaly/service/operations/merge_test.go
+++ b/internal/gitaly/service/operations/merge_test.go
@@ -913,38 +913,23 @@ func testUserMergeBranchConflict(t *testing.T, ctx context.Context) {
 
 	ctx, cfg, repoProto, repoPath, client := setupOperationsService(t, ctx)
 
-	const baseBranch = "base"
 	const mergeIntoBranch = "mergeIntoBranch"
 	const mergeFromBranch = "mergeFromBranch"
 	const conflictingFile = "file"
 
-	baseCommit := gittest.WriteCommit(t, cfg, repoPath, gittest.WithBranch(baseBranch), gittest.WithTreeEntries(gittest.TreeEntry{
+	baseCommit := gittest.WriteCommit(t, cfg, repoPath, gittest.WithBranch(mergeIntoBranch), gittest.WithTreeEntries(gittest.TreeEntry{
 		Mode: "100644", Path: conflictingFile, Content: "data",
 	}))
 
 	gittest.Exec(t, cfg, "-C", repoPath, "branch", mergeFromBranch, baseCommit.String())
 
-	divergedInto := gittest.WriteCommit(
-		t,
-		cfg,
-		repoPath,
-		gittest.WithBranch(mergeIntoBranch),
-		gittest.WithParents(baseCommit),
-		gittest.WithTreeEntries(gittest.TreeEntry{
-			Mode: "100644", Path: conflictingFile, Content: "data-1",
-		}),
-	)
+	divergedInto := gittest.WriteCommit(t, cfg, repoPath, gittest.WithBranch(mergeIntoBranch), gittest.WithTreeEntries(gittest.TreeEntry{
+		Mode: "100644", Path: conflictingFile, Content: "data-1",
+	}))
 
-	divergedFrom := gittest.WriteCommit(
-		t,
-		cfg,
-		repoPath,
-		gittest.WithBranch(mergeFromBranch),
-		gittest.WithParents(baseCommit),
-		gittest.WithTreeEntries(gittest.TreeEntry{
-			Mode: "100644", Path: conflictingFile, Content: "data-2",
-		}),
-	)
+	divergedFrom := gittest.WriteCommit(t, cfg, repoPath, gittest.WithBranch(mergeFromBranch), gittest.WithTreeEntries(gittest.TreeEntry{
+		Mode: "100644", Path: conflictingFile, Content: "data-2",
+	}))
 
 	mergeBidi, err := client.UserMergeBranch(ctx)
 	require.NoError(t, err)