Add --git-dir param to modularization_stats.py preemptively

https://chromium-review.googlesource.com/c/chromium/src/+/2538118
will use this parameter, but it needs to be added preemptively
so that the recipe can be updated preemptively.

Bug: 1146478
Change-Id: Ie9a3bc8d1885ae42fb921844bda4ae3131230ba5
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2538312Reviewed-by: Mohamed Heikal <mheikal@chromium.org>
Commit-Queue: Henrique Nakashima <hnakashima@chromium.org>
Cr-Commit-Position: refs/heads/master@{#827845}

tools/android/dependency_analysis/modularization_stats.py

@@ -86,6 +86,13 @@ def main():
         required=True,
         help='Path to the JSON file containing the dependency graph. '
         'See the README on how to generate this file.')
+    # TODO(crbug.com/1146478): --git-dir is currently unused, but will be used
+    # to calculate % LoCs in modularized files.
+    arg_parser.add_argument(
+        '--git-dir',
+        type=str,
+        help='Root directory of the git repo to look into. '
+        'If not specified, use the current directory.')
     arg_parser.add_argument(
         '-o',
         '--output',