support relative worktree paths (git 2.48+ worktree.useRelativePaths)

git 2.48 introduced the `worktree.useRelativePaths` config option,
which causes `git worktree add` to write a relative `gitdir` into the
worktree's `.git` file.

Resolve the relative `gitdir` against the worktree directory before
normalizing it. Absolute paths are unaffected because `os.path.join`
ignores the prefix when joined with an absolute path.

Author: elovelan

git/repo/base.py

@@ -295,7 +295,8 @@ def __init__(
                 sm_gitpath = find_worktree_git_dir(dotgit)
 
             if sm_gitpath is not None:
-                git_dir = osp.normpath(sm_gitpath)
+                # worktrees can use relative paths as of Git 2.48, so we join to curpath
+                git_dir = osp.normpath(osp.join(curpath, sm_gitpath))
                 self._working_tree_dir = curpath
                 break
 

test/test_repo.py

@@ -1094,7 +1094,7 @@ def test_is_valid_object(self):
         self.assertFalse(repo.is_valid_object(tag_sha, "commit"))
 
     @with_rw_directory
-    def test_git_work_tree_dotgit(self, rw_dir):
+    def test_git_work_tree_dotgit(self, rw_dir, use_relative_paths=False):
         """Check that we find .git as a worktree file and find the worktree
         based on it."""
         git = Git(rw_dir)
@@ -1106,7 +1106,11 @@ def test_git_work_tree_dotgit(self, rw_dir):
         worktree_path = join_path_native(rw_dir, "worktree_repo")
         if Git.is_cygwin():
             worktree_path = cygpath(worktree_path)
-        rw_master.git.worktree("add", worktree_path, branch.name)
+        wt_add_kwargs = {"insert_kwargs_after": "add"}
+        # relative worktree paths introduced in git 2.48.0
+        if use_relative_paths and git.version_info[:3] >= (2, 48, 0):
+            wt_add_kwargs["relative_paths"] = True
+        rw_master.git.worktree("add", worktree_path, branch.name, **wt_add_kwargs)
 
         # This ensures that we can read the repo's gitdir correctly.
         repo = Repo(worktree_path)
@@ -1124,6 +1128,15 @@ def test_git_work_tree_dotgit(self, rw_dir):
 
         self.assertIsInstance(repo.heads["aaaaaaaa"], Head)
 
+    def test_git_work_tree_dotgit_relative(self):
+        """Check that we find .git as a worktree file containing a relative path
+        and find the worktree based on it."""
+        if Git().version_info[:3] < (2, 48, 0):
+            pytest.skip("relative worktree feature unsupported, needs git 2.48.0 or later")
+        # this class inherits from TestCase so we can't use pytest.mark.parametrize on
+        # test_git_work_tree_dotgit; delegate instead
+        self.test_git_work_tree_dotgit(use_relative_paths=True)
+
     @with_rw_directory
     def test_git_work_tree_env(self, rw_dir):
         """Check that we yield to GIT_WORK_TREE."""