Fix apparent bug when running the GitDiff tool

aider/repo.py

@@ -417,14 +417,17 @@ def get_diffs(self, fnames=None):
         except ANY_GIT_ERROR as err:
             self.io.tool_error(f"Unable to diff: {err}")
 
-    def diff_commits(self, pretty, from_commit, to_commit):
+    def diff_commits(self, pretty, from_commit, to_commit=None):
         args = []
         if pretty:
             args += ["--color"]
         else:
             args += ["--color=never"]
 
-        args += [from_commit, to_commit]
+        if to_commit is not None:
+            args += [from_commit, to_commit]
+        else:
+            args += [from_commit]
         diffs = self.repo.git.diff(*args, stdout_as_string=False).decode(
             self.io.encoding, "replace"
         )

aider/tools/git_branch.py

@@ -113,12 +113,17 @@ def execute(
                 args.extend(["--format", format])
 
             # Execute git command
-            result = coder.repo.repo.git.branch(*args)
+            result = coder.repo.repo.git.branch(*args).strip()
 
             # If no result and show_current was used, get current branch directly
             if not result and show_current:
-                current_branch = coder.repo.repo.active_branch.name
-                return current_branch
+                try:
+                    head = coder.repo.repo.head
+                    if head.is_detached:
+                        return "HEAD (detached)"
+                    return coder.repo.repo.active_branch.name
+                except ANY_GIT_ERROR:
+                    return "No current branch found."
 
             return result if result else "No branches found matching the criteria."
 

aider/tools/git_diff.py

@@ -36,7 +36,8 @@ def execute(cls, coder, branch=None):
 
         try:
             if branch:
-                diff = coder.repo.diff_commits(False, branch, "HEAD")
+                # Diff working tree against the requested branch/commit
+                diff = coder.repo.diff_commits(False, branch, None)
             else:
                 diff = coder.repo.diff_commits(False, "HEAD", None)
 

tests/tools/test_git_branch.py

@@ -0,0 +1,51 @@
+from pathlib import Path
+from types import SimpleNamespace
+
+import git
+
+from aider.io import InputOutput
+from aider.repo import GitRepo
+from aider.tools import git_branch
+from aider.utils import GitTemporaryDirectory
+
+
+def _make_repo():
+    repo = git.Repo()
+    repo.config_writer().set_value("commit", "gpgsign", "false").release()
+    return repo
+
+
+def test_gitbranch_show_current_returns_branch_name():
+    with GitTemporaryDirectory():
+        repo = _make_repo()
+        Path("file.txt").write_text("content\n")
+        repo.git.add("file.txt")
+        repo.git.commit("-m", "init")
+        repo.git.checkout("-b", "feature")
+
+        io = InputOutput()
+        git_repo = GitRepo(io, None, ".")
+        coder = SimpleNamespace(repo=git_repo, io=io)
+
+        result = git_branch.Tool.execute(coder, show_current=True)
+
+        assert result.strip() == "feature"
+
+
+def test_gitbranch_show_current_handles_detached_head():
+    with GitTemporaryDirectory():
+        repo = _make_repo()
+        Path("file.txt").write_text("content\n")
+        repo.git.add("file.txt")
+        repo.git.commit("-m", "init")
+
+        commit_sha = repo.head.commit.hexsha
+        repo.git.checkout(commit_sha)
+
+        io = InputOutput()
+        git_repo = GitRepo(io, None, ".")
+        coder = SimpleNamespace(repo=git_repo, io=io)
+
+        result = git_branch.Tool.execute(coder, show_current=True)
+
+        assert result.strip() == "HEAD (detached)"

tests/tools/test_git_diff.py

@@ -0,0 +1,29 @@
+from pathlib import Path
+from types import SimpleNamespace
+
+import git
+
+from aider.io import InputOutput
+from aider.repo import GitRepo
+from aider.tools import git_diff
+from aider.utils import GitTemporaryDirectory
+
+
+def test_gitdiff_head_argument_includes_working_tree_changes():
+    with GitTemporaryDirectory():
+        repo = git.Repo()
+        fname = Path("example.txt")
+        fname.write_text("original\n")
+        repo.git.add(str(fname))
+        repo.config_writer().set_value("commit", "gpgsign", "false").release()
+        repo.git.commit("-m", "initial")
+
+        fname.write_text("updated\n")
+
+        io = InputOutput()
+        git_repo = GitRepo(io, None, ".")
+        coder = SimpleNamespace(repo=git_repo, io=io)
+
+        result = git_diff.Tool.execute(coder, branch="HEAD")
+
+        assert "updated" in result