Add Amend option to CommitOptions

Adds an Amend option to CommitOptions that behaves like git --amend.
This change includes modifications to the Validate function to disallow
a Commit call with both Amend and either Parents or All enabled.

1 files changed, 29 insertions, 12 deletions

diff --git a/worktree_commit.go b/worktree_commit.go
index dc79569..86320d8 100644
--- a/worktree_commit.go
+++ b/worktree_commit.go
@@ -29,22 +29,39 @@ func (w *Worktree) Commit(msg string, opts *CommitOptions) (plumbing.Hash, error
 		}
 	}
 
-	idx, err := w.r.Storer.Index()
-	if err != nil {
-		return plumbing.ZeroHash, err
-	}
+	var treeHash plumbing.Hash
 
-	h := &buildTreeHelper{
-		fs: w.Filesystem,
-		s:  w.r.Storer,
-	}
+	if opts.Amend {
+		head, err := w.r.Head()
+		if err != nil {
+			return plumbing.ZeroHash, err
+		}
 
-	tree, err := h.BuildTree(idx)
-	if err != nil {
-		return plumbing.ZeroHash, err
+		t, err := w.getTreeFromCommitHash(head.Hash())
+		if err != nil {
+			return plumbing.ZeroHash, err
+		}
+
+		treeHash = t.Hash
+		opts.Parents = []plumbing.Hash{head.Hash()}
+	}else {
+		idx, err := w.r.Storer.Index()
+		if err != nil {
+			return plumbing.ZeroHash, err
+		}
+
+		h := &buildTreeHelper{
+			fs: w.Filesystem,
+			s:  w.r.Storer,
+		}
+
+		treeHash, err = h.BuildTree(idx)
+		if err != nil {
+			return plumbing.ZeroHash, err
+		}
 	}
 
-	commit, err := w.buildCommitObject(msg, opts, tree)
+	commit, err := w.buildCommitObject(msg, opts, treeHash)
 	if err != nil {
 		return plumbing.ZeroHash, err
 	}