Revert "Set --git-dir for git commands that may be executed in bare gits."

This reverts commit d9011c559b51f3edf9878196b595222def18f309.

Reason for revert: Breaks ChromeOS staging builders: b/296139378

Original change's description:
> Set --git-dir for git commands that may be executed in bare gits.
>
> Bug:b/294415576
> Change-Id: I18ca8ebebf95e1c31e30aa1f5d62da3467df940f
> Reviewed-on: https://chromium-review.googlesource.com/c/chromium/tools/depot_tools/+/4778199
> Auto-Submit: Joanna Wang <jojwang@chromium.org>
> Reviewed-by: Gavin Mak <gavinmak@google.com>
> Commit-Queue: Joanna Wang <jojwang@chromium.org>

Bug: b/294415576
Change-Id: Ie16f16a405fbdea4d925e03a0cfd1ac0260bb2d8
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/tools/depot_tools/+/4784102
Commit-Queue: Jack Neus <jackneus@google.com>
Bot-Commit: Rubber Stamper <rubber-stamper@appspot.gserviceaccount.com>
Reviewed-by: Joanna Wang <jojwang@chromium.org>

git_cache.py

@@ -234,8 +234,6 @@ class Mirror(object):
   def RunGit(self, cmd, print_stdout=True, **kwargs):
     """Run git in a subprocess."""
     cwd = kwargs.setdefault('cwd', self.mirror_path)
-    if "--git-dir" not in cmd:
-      cmd = ['--git-dir', cwd] + cmd
     kwargs.setdefault('print_stdout', False)
     if print_stdout:
       kwargs.setdefault('filter_fn', self.print)
@@ -448,12 +446,11 @@ class Mirror(object):
         # Start with a bare git dir.
         self.RunGit(['init', '--bare'], cwd=self.mirror_path)
         # Set appropriate symbolic-ref
-        remote_info = exponential_backoff_retry(lambda: subprocess.check_output(
-            [
-                self.git_exe, '--git-dir', self.mirror_path, 'remote', 'show',
-                self.url
-            ],
-            cwd=self.mirror_path).decode('utf-8', 'ignore').strip())
+        remote_info = exponential_backoff_retry(
+            lambda: subprocess.check_output(
+                [self.git_exe, 'remote', 'show', self.url],
+                cwd=self.mirror_path).decode('utf-8', 'ignore').strip()
+        )
         default_branch_regexp = re.compile(r'HEAD branch: (.*)$')
         m = default_branch_regexp.search(remote_info, re.MULTILINE)
         if m:
@@ -467,12 +464,13 @@ class Mirror(object):
             len(pack_files))
 
   def _fetch(self,
+             rundir,
              verbose,
              depth,
              no_fetch_tags,
              reset_fetch_config,
              prune=True):
-    self.config(self.mirror_path, reset_fetch_config)
+    self.config(rundir, reset_fetch_config)
 
     fetch_cmd = ['fetch']
     if verbose:
@@ -485,18 +483,14 @@ class Mirror(object):
       fetch_cmd.append('--prune')
     fetch_cmd.append('origin')
 
-    fetch_specs = subprocess.check_output([
-        self.git_exe, '--git-dir', self.mirror_path, 'config', '--get-all',
-        'remote.origin.fetch'
-    ],
-                                          cwd=self.mirror_path).decode(
-                                              'utf-8',
-                                              'ignore').strip().splitlines()
+    fetch_specs = subprocess.check_output(
+        [self.git_exe, 'config', '--get-all', 'remote.origin.fetch'],
+        cwd=rundir).decode('utf-8', 'ignore').strip().splitlines()
     for spec in fetch_specs:
       try:
         self.print('Fetching %s' % spec)
         with self.print_duration_of('fetch %s' % spec):
-          self.RunGit(fetch_cmd + [spec], retry=True)
+          self.RunGit(fetch_cmd + [spec], cwd=rundir, retry=True)
       except subprocess.CalledProcessError:
         if spec == '+refs/heads/*:refs/heads/*':
           raise ClobberNeeded()  # Corrupted cache.
@@ -505,7 +499,7 @@ class Mirror(object):
       self.print('Fetching %s' % commit)
       try:
         with self.print_duration_of('fetch %s' % commit):
-          self.RunGit(['fetch', 'origin', commit], retry=True)
+          self.RunGit(['fetch', 'origin', commit], cwd=rundir, retry=True)
       except subprocess.CalledProcessError:
         logging.warning('Fetch of %s failed' % commit)
 
@@ -525,7 +519,8 @@ class Mirror(object):
     with lockfile.lock(self.mirror_path, lock_timeout):
       try:
         self._ensure_bootstrapped(depth, bootstrap, reset_fetch_config)
-        self._fetch(verbose, depth, no_fetch_tags, reset_fetch_config)
+        self._fetch(self.mirror_path, verbose, depth, no_fetch_tags,
+                    reset_fetch_config)
       except ClobberNeeded:
         # This is a major failure, we need to clean and force a bootstrap.
         gclient_utils.rmtree(self.mirror_path)
@@ -534,7 +529,8 @@ class Mirror(object):
                                   bootstrap,
                                   reset_fetch_config,
                                   force=True)
-        self._fetch(verbose, depth, no_fetch_tags, reset_fetch_config)
+        self._fetch(self.mirror_path, verbose, depth, no_fetch_tags,
+                    reset_fetch_config)
 
   def update_bootstrap(self, prune=False, gc_aggressive=False):
     # NOTE: There have been cases where repos were being recursively uploaded

tests/git_cache_test.py

@@ -92,10 +92,8 @@ class GitCacheTest(unittest.TestCase):
     # Add a bad refspec to the cache's fetch config.
     cache_dir = os.path.join(
         self.cache_dir, mirror.UrlToCacheDir(self.origin_dir))
-    self.git([
-        '--git-dir', cache_dir, 'config', '--add', 'remote.origin.fetch',
-        '+refs/heads/foo:refs/heads/foo'
-    ],
+    self.git(['config', '--add', 'remote.origin.fetch',
+              '+refs/heads/foo:refs/heads/foo'],
              cwd=cache_dir)
 
     mirror.populate(reset_fetch_config=True)