Add unit tests for git_find_releases

R=ehmaldonado@chromium.org

Change-Id: Ib11ada368fda13bbef62c8be26ddb9c78a528a92
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/tools/depot_tools/+/2107839
Reviewed-by: Edward Lesmes <ehmaldonado@chromium.org>
Commit-Queue: Josip Sokcevic <sokcevic@google.com>

git_find_releases.py

@@ -35,9 +35,9 @@ def GetMergesForCommit(sha1):
                   'cherry picked from commit %s' % sha1).splitlines()]
 
 
-def main():
+def main(args):
   parser = optparse.OptionParser(usage=sys.modules[__name__].__doc__)
-  _, args = parser.parse_args()
+  _, args = parser.parse_args(args)
 
   if len(args) == 0:
     parser.error('Need at least one commit.')
@@ -61,7 +61,7 @@ def main():
 
 if __name__ == '__main__':
   try:
-    sys.exit(main())
+    sys.exit(main(sys.argv[1:]))
   except KeyboardInterrupt:
     sys.stderr.write('interrupted\n')
     sys.exit(1)