Fix GetCommitFileStatus on merge commit

Add new test repo repo6_merge

Author: tdesveaux

modules/git/commit.go

@@ -521,7 +521,7 @@ func GetCommitFileStatus(ctx context.Context, repoPath, commitID string) (*Commi
 	}()
 
 	stderr := new(bytes.Buffer)
-	err := NewCommand(ctx, "log", "--name-status", "-c", "--pretty=format:", "--parents", "--no-renames", "-z", "-1").AddDynamicArguments(commitID).Run(&RunOpts{
+	err := NewCommand(ctx, "log", "--name-status", "-m", "--pretty=format:", "--first-parent", "--no-renames", "-z", "-1").AddDynamicArguments(commitID).Run(&RunOpts{
 		Dir:    repoPath,
 		Stdout: w,
 		Stderr: stderr,

modules/git/commit_test.go

@@ -255,3 +255,26 @@ func TestParseCommitFileStatus(t *testing.T) {
 		assert.Equal(t, kase.modified, fileStatus.Modified)
 	}
 }
+
+func TestGetCommitFileStatusMerges(t *testing.T) {
+	bareRepo1Path := filepath.Join(testReposDir, "repo6_merge")
+
+	commitFileStatus, err := GetCommitFileStatus(DefaultContext, bareRepo1Path, "022f4ce6214973e018f02bf363bf8a2e3691f699")
+	assert.NoError(t, err)
+
+	expected := CommitFileStatus{
+		[]string{
+			"add_file.txt",
+		},
+		[]string{
+			"to_remove.txt",
+		},
+		[]string{
+			"to_modify.txt",
+		},
+	}
+
+	assert.Equal(t, commitFileStatus.Added, expected.Added)
+	assert.Equal(t, commitFileStatus.Removed, expected.Removed)
+	assert.Equal(t, commitFileStatus.Modified, expected.Modified)
+}

modules/git/tests/repos/repo6_merge/HEAD

@@ -0,0 +1 @@
+ref: refs/heads/main

modules/git/tests/repos/repo6_merge/config

@@ -0,0 +1,5 @@
+[core]
+	repositoryformatversion = 0
+	filemode = false
+	bare = true
+	ignorecase = true

modules/git/tests/repos/repo6_merge/description

@@ -0,0 +1 @@
+Unnamed repository; edit this file 'description' to name the repository.

modules/git/tests/repos/repo6_merge/info/exclude

@@ -0,0 +1,6 @@
+# git ls-files --others --exclude-from=.git/info/exclude
+# Lines that start with '#' are comments.
+# For a project mostly in C, the following would be a good set of
+# exclude patterns (uncomment them if you want to use them):
+# *.[oa]
+# *~

modules/git/tests/repos/repo6_merge/objects/02/2f4ce6214973e018f02bf363bf8a2e3691f699

@@ -0,0 +1,2 @@
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