git: worktree_commit, Modify checking empty commit. Fixes go-git#723

Author: onee-only

worktree_commit.go

@@ -38,8 +38,6 @@ func (w *Worktree) Commit(msg string, opts *CommitOptions) (plumbing.Hash, error
 		}
 	}
 
-	var treeHash plumbing.Hash
-
 	if opts.Amend {
 		head, err := w.r.Head()
 		if err != nil {
@@ -61,16 +59,34 @@ func (w *Worktree) Commit(msg string, opts *CommitOptions) (plumbing.Hash, error
 		return plumbing.ZeroHash, err
 	}
 
+	// First handle the case of the first commit in the repository being empty.
+	if len(opts.Parents) == 0 && len(idx.Entries) == 0 && !opts.AllowEmptyCommits {
+		return plumbing.ZeroHash, ErrEmptyCommit
+	}
+
 	h := &buildTreeHelper{
 		fs: w.Filesystem,
 		s:  w.r.Storer,
 	}
 
-	treeHash, err = h.BuildTree(idx, opts)
+	treeHash, err := h.BuildTree(idx, opts)
 	if err != nil {
 		return plumbing.ZeroHash, err
 	}
 
+	previousTree := plumbing.ZeroHash
+	if len(opts.Parents) > 0 {
+		parentCommit, err := w.r.CommitObject(opts.Parents[0])
+		if err != nil {
+			return plumbing.ZeroHash, err
+		}
+		previousTree = parentCommit.TreeHash
+	}
+
+	if treeHash == previousTree && !opts.AllowEmptyCommits {
+		return plumbing.ZeroHash, ErrEmptyCommit
+	}
+
 	commit, err := w.buildCommitObject(msg, opts, treeHash)
 	if err != nil {
 		return plumbing.ZeroHash, err
@@ -175,10 +191,6 @@ type buildTreeHelper struct {
 // BuildTree builds the tree objects and push its to the storer, the hash
 // of the root tree is returned.
 func (h *buildTreeHelper) BuildTree(idx *index.Index, opts *CommitOptions) (plumbing.Hash, error) {
-	if len(idx.Entries) == 0 && (opts == nil || !opts.AllowEmptyCommits) {
-		return plumbing.ZeroHash, ErrEmptyCommit
-	}
-
 	const rootNode = ""
 	h.trees = map[string]*object.Tree{rootNode: {}}
 	h.entries = map[string]*object.TreeEntry{}