Repo: handle worktrees better

This makes Repo("foo") work when foo/.git is a file of the form created
by "git worktree add", i.e. it's a text file that says:

gitdir: /home/me/project/.git/worktrees/bar

and where /home/me/project/.git/ is the nominal gitdir, but
/home/me/project/.git/worktrees/bar has this worktree's HEAD etc and a
"gitdir" file that contains the path of foo/.git .

Signed-off-by: Peter Jones <pjones@redhat.com>

2 files changed, 51 insertions, 12 deletions

diff --git a/git/test/test_fun.py b/git/test/test_fun.py
index b472fe19..5e32a1f9 100644
--- a/git/test/test_fun.py
+++ b/git/test/test_fun.py
@@ -1,10 +1,14 @@
 from io import BytesIO
 from stat import S_IFDIR, S_IFREG, S_IFLNK
+from os import stat
+import os.path as osp
+
 try:
-    from unittest import skipIf
+    from unittest import skipIf, SkipTest
 except ImportError:
-    from unittest2 import skipIf
+    from unittest2 import skipIf, SkipTest
 
+from git import Git
 from git.compat import PY3
 from git.index import IndexFile
 from git.index.fun import (
@@ -14,13 +18,18 @@ from git.objects.fun import (
     traverse_tree_recursive,
     traverse_trees_recursive,
     tree_to_stream,
-    tree_entries_from_data
+    tree_entries_from_data,
+)
+from git.repo.fun import (
+    find_worktree_git_dir
 )
 from git.test.lib import (
+    assert_true,
     TestBase,
-    with_rw_repo
+    with_rw_repo,
+    with_rw_directory
 )
-from git.util import bin_to_hex
+from git.util import bin_to_hex, cygpath, join_path_native
 from gitdb.base import IStream
 from gitdb.typ import str_tree_type
 
@@ -254,6 +263,29 @@ class TestFun(TestBase):
             assert entries
         # END for each commit
 
+    @with_rw_directory
+    def test_linked_worktree_traversal(self, rw_dir):
+        """Check that we can identify a linked worktree based on a .git file"""
+        git = Git(rw_dir)
+        if git.version_info[:3] < (2, 5, 1):
+            raise SkipTest("worktree feature unsupported")
+
+        rw_master = self.rorepo.clone(join_path_native(rw_dir, 'master_repo'))
+        branch = rw_master.create_head('aaaaaaaa')
+        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)
+
+        dotgit = osp.join(worktree_path, ".git")
+        statbuf = stat(dotgit)
+        assert_true(statbuf.st_mode & S_IFREG)
+
+        gitdir = find_worktree_git_dir(dotgit)
+        self.assertIsNotNone(gitdir)
+        statbuf = stat(gitdir)
+        assert_true(statbuf.st_mode & S_IFDIR)
+
     @skipIf(PY3, 'odd types returned ... maybe figure it out one day')
     def test_tree_entries_from_data_with_failing_name_decode_py2(self):
         r = tree_entries_from_data(b'100644 \x9f\0aaa')
diff --git a/git/test/test_repo.py b/git/test/test_repo.py
index 86019b73..a6be4e66 100644
--- a/git/test/test_repo.py
+++ b/git/test/test_repo.py
@@ -22,6 +22,7 @@ from git import (
     NoSuchPathError,
     Head,
     Commit,
+    Object,
     Tree,
     IndexFile,
     Git,
@@ -911,22 +912,28 @@ class TestRepo(TestBase):
             self.assertRaises(GitCommandError, repo.is_ancestor, i, j)
 
     @with_rw_directory
-    def test_work_tree_unsupported(self, rw_dir):
+    def test_git_work_tree_dotgit(self, rw_dir):
+        """Check that we find .git as a worktree file and find the worktree
+        based on it."""
         git = Git(rw_dir)
         if git.version_info[:3] < (2, 5, 1):
             raise SkipTest("worktree feature unsupported")
 
         rw_master = self.rorepo.clone(join_path_native(rw_dir, 'master_repo'))
-        rw_master.git.checkout('HEAD~10')
+        branch = rw_master.create_head('aaaaaaaa')
         worktree_path = join_path_native(rw_dir, 'worktree_repo')
         if Git.is_cygwin():
             worktree_path = cygpath(worktree_path)
-        try:
-            rw_master.git.worktree('add', worktree_path, 'master')
-        except Exception as ex:
-            raise AssertionError(ex, "It's ok if TC not running from `master`.")
+        rw_master.git.worktree('add', worktree_path, branch.name)
+
+        # this ensures that we can read the repo's gitdir correctly
+        repo = Repo(worktree_path)
+        self.assertIsInstance(repo, Repo)
 
-        self.failUnlessRaises(InvalidGitRepositoryError, Repo, worktree_path)
+        # this ensures we're able to actually read the refs in the tree, which
+        # means we can read commondir correctly.
+        commit = repo.head.commit
+        self.assertIsInstance(commit, Object)
 
     @with_rw_directory
     def test_git_work_tree_env(self, rw_dir):