fix: handle detached head cases

Author: Simon Prochazka

.gitignore

@@ -1,3 +1,4 @@
 testdata/commits_on_branch/
 testdata/git_tags/
 testdata/annotated_git_tags_mix/
+testdata/detached_head/

branch_diff_commits.go

@@ -14,7 +14,7 @@ func (g *Git) BranchDiffCommits(branchA string, branchB string) ([]Hash, error)
 	// The ^branchB syntax excludes all commits reachable from branchB
 	output, err := g.runGitCommand("log", "--format=%H", branchA, "^"+branchB)
 	if err != nil {
-		return nil, fmt.Errorf("Failed comparing branches %v and %v: %v", branchA, branchB, err)
+		return nil, fmt.Errorf("failed comparing branches %v and %v: %v", branchA, branchB, err)
 	}
 
 	var diffCommits []Hash

branch_diff_commits_test.go

@@ -37,3 +37,25 @@ func TestBranchDiffCommitsWithMasterMerge(t *testing.T) {
 	assert.Equal(t, err, nil)
 
 }
+
+func TestBranchDiffCommitsDetachedHead(t *testing.T) {
+	testGit, err := OpenGit("./testdata/detached_head")
+	assert.NoError(t, err)
+
+	// Verify we're in detached HEAD state
+	currentBranch, err := testGit.CurrentBranch()
+	assert.NoError(t, err)
+	assert.Equal(t, "HEAD", currentBranch.Name())
+
+	// BranchDiffCommits should work even in detached HEAD state
+	// Compare origin/master (which is ahead) to HEAD (which is at second commit)
+	commits, err := testGit.BranchDiffCommits("origin/master", "HEAD")
+
+	assert.NoError(t, err)
+	// origin/master has one commit ahead of HEAD (the third commit)
+	assert.Equal(t, 1, len(commits))
+
+	commit, err := testGit.Commit(commits[0])
+	assert.NoError(t, err)
+	assert.Equal(t, "third commit\n", commit.Message)
+}

commits_between_test.go

@@ -68,3 +68,34 @@ func TestToFromEqual(t *testing.T) {
 	assert.Equal(t, 0, len(commits))
 	assert.NoError(t, err)
 }
+
+func TestCommitsBetweenDetachedHead(t *testing.T) {
+	testGit, err := OpenGit("./testdata/detached_head")
+	assert.NoError(t, err)
+
+	// Verify we're in detached HEAD state
+	currentBranch, err := testGit.CurrentBranch()
+	assert.NoError(t, err)
+	assert.Equal(t, "HEAD", currentBranch.Name())
+
+	// Get HEAD commit hash (second commit)
+	headHash := currentBranch.Hash()
+
+	// Get origin/master commit hash (third commit)
+	masterHashStr, err := testGit.runGitCommand("rev-parse", "origin/master")
+	assert.NoError(t, err)
+	masterHash, err := NewHash(masterHashStr)
+	assert.NoError(t, err)
+
+	// CommitsBetween should work even in detached HEAD state
+	// Get commits between HEAD (second commit) and origin/master (third commit)
+	commits, err := testGit.CommitsBetween(masterHash, headHash)
+
+	assert.NoError(t, err)
+	// Should have 1 commit (the third commit)
+	assert.Equal(t, 1, len(commits))
+
+	commit, err := testGit.Commit(commits[0])
+	assert.NoError(t, err)
+	assert.Equal(t, "third commit\n", commit.Message)
+}

commits_on_branch_test.go

@@ -27,3 +27,32 @@ func TestCommitsOnBranch(t *testing.T) {
 
 	assert.Equal(t, "test commit on master\n", lastCommit.Message)
 }
+
+func TestCommitsOnBranchDetachedHead(t *testing.T) {
+	testGit, err := OpenGit("./testdata/detached_head")
+	assert.NoError(t, err)
+
+	// Verify we're in detached HEAD state
+	currentBranch, err := testGit.CurrentBranch()
+	assert.NoError(t, err)
+	assert.Equal(t, "HEAD", currentBranch.Name())
+
+	// Get HEAD commit hash
+	headHash := currentBranch.Hash()
+
+	// CommitsOnBranch should work even in detached HEAD state
+	// It takes a commit hash, so HEAD state doesn't matter
+	commits, err := testGit.CommitsOnBranch(headHash)
+
+	assert.NoError(t, err)
+	// Should have 2 commits (second commit and first commit)
+	assert.Equal(t, 2, len(commits))
+
+	commit, err := testGit.Commit(commits[0])
+	assert.NoError(t, err)
+	assert.Equal(t, "second commit\n", commit.Message)
+
+	lastCommit, err := testGit.Commit(commits[1])
+	assert.NoError(t, err)
+	assert.Equal(t, "first commit\n", lastCommit.Message)
+}

current_branch.go

@@ -1,22 +1,24 @@
 package git
 
-// CurrentBranch returns the reference HEAD is at right now
+// CurrentBranch returns the reference HEAD is at right now.
+// In detached HEAD state, it returns a reference with name "HEAD".
 func (g *Git) CurrentBranch() (*Reference, error) {
-	// Get the symbolic ref name
-	refName, err := g.runGitCommand("symbolic-ref", "HEAD")
+	// Get the commit hash first (works in both normal and detached HEAD state)
+	hashStr, err := g.runGitCommand("rev-parse", "HEAD")
 	if err != nil {
 		return nil, err
 	}
 
-	// Get the commit hash
-	hashStr, err := g.runGitCommand("rev-parse", "HEAD")
+	hash, err := NewHash(hashStr)
 	if err != nil {
 		return nil, err
 	}
 
-	hash, err := NewHash(hashStr)
+	// Try to get the symbolic ref name (fails in detached HEAD state)
+	refName, err := g.runGitCommand("symbolic-ref", "HEAD")
 	if err != nil {
-		return nil, err
+		// In detached HEAD state, use "HEAD" as the reference name
+		refName = "HEAD"
 	}
 
 	return NewReference(refName, hash), nil

current_branch_test.go

@@ -18,3 +18,16 @@ func TestCurrentBranch(t *testing.T) {
 	assert.NoError(t, err)
 	assert.Equal(t, "refs/heads/my-branch", currentBranch.Name())
 }
+
+func TestCurrentBranchDetachedHead(t *testing.T) {
+	testGit, err := OpenGit("./testdata/detached_head")
+	assert.NoError(t, err)
+
+	currentBranch, err := testGit.CurrentBranch()
+
+	assert.NoError(t, err)
+	assert.Equal(t, "HEAD", currentBranch.Name())
+	
+	// Verify it has a valid commit hash
+	assert.NotEmpty(t, currentBranch.Hash().String())
+}

latest_commit_on_branch_test.go

@@ -19,3 +19,19 @@ func TestLatestCommitOnBranch(t *testing.T) {
 	assert.Equal(t, "third commit on new branch\n", commit.Message)
 	assert.Equal(t, err, nil)
 }
+
+func TestLatestCommitOnBranchDetachedHead(t *testing.T) {
+	testGit, err := OpenGit("./testdata/detached_head")
+	assert.NoError(t, err)
+
+	// Verify we're in detached HEAD state
+	currentBranch, err := testGit.CurrentBranch()
+	assert.NoError(t, err)
+	assert.Equal(t, "HEAD", currentBranch.Name())
+
+	// LatestCommitOnBranch should work even in detached HEAD state
+	commit, err := testGit.LatestCommitOnBranch("origin/master")
+
+	assert.NoError(t, err)
+	assert.Equal(t, "third commit\n", commit.Message)
+}

testdata/detached_head.bundle

@@ -16,3 +16,8 @@ echo 'testdata/annotated_git_tags_mix/ directory does not exist at the root; cre
 rm -rf annotated_git_tags_mix
 git clone annotated_git_tags_mix.bundle
 echo 'done'
+
+echo 'testdata/detached_head/ directory does not exist at the root; creating...'
+rm -rf detached_head
+git clone detached_head.bundle
+echo 'done'