--- a/git/commands/git-mozreview
+++ b/git/commands/git-mozreview
@@ -53,32 +53,28 @@ CLIENT_CAPABILITIES = {
     'bzapikeys',
     'jsonproto',
     'commitid',
 }
 
 MAX_REVIEW_COMMITS = 100
 
 
-git_dir = os.environ.get('GIT_COMMON_DIR')
-if not git_dir:
-    git_dir = os.environ.get('GIT_DIR')
-if not git_dir:
-    git_dir = subprocess.check_output(
-            ['git', 'rev-parse', '--no-flags', '--git-common-dir']).rstrip('\n')
-    # Up to version 2.8, git rev-parse --git-common-dir returns '.git' when in
-    # a subdirectory of the main work tree. In 2.8, it returns 'subdir/.git',
-    # which is wrong as well.
-    # In both cases, we can just fall through to --git-dir.
-    # When running from a separate work tree, --git-common-dir always returns
-    # an absolute path. When running from the main work tree and
-    # --git-common-dir returns an absolute path, it's correct. So we can assume
-    # that when it returns a relative path, we can use --git-dir instead.
-    if not os.path.isabs(git_dir):
-        git_dir = None
+git_dir = subprocess.check_output(
+        ['git', 'rev-parse', '--no-flags', '--git-common-dir']).rstrip('\n')
+# Up to version 2.8, git rev-parse --git-common-dir returns '.git' when in
+# a subdirectory of the main work tree. In 2.8, it returns 'subdir/.git',
+# which is wrong as well.
+# In both cases, we can just fall through to --git-dir.
+# When running from a separate work tree, --git-common-dir always returns
+# an absolute path. When running from the main work tree and
+# --git-common-dir returns an absolute path, it's correct. So we can assume
+# that when it returns a relative path, we can use --git-dir instead.
+if not os.path.isabs(git_dir):
+    git_dir = None
 # git versions before 2.5 don't support --git-common-dir, so fallback to
 # --git-dir
 if not git_dir:
     git_dir = subprocess.check_output(
             ['git', 'rev-parse', '--git-dir']).rstrip('\n')
 
 
 def gethgui():