repo: update launcher to v2.21

Change-Id: I47bfd073a10ac72572d8e4b67650958f5f119fdf
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/tools/depot_tools/+/3438329
Auto-Submit: Mike Frysinger <vapier@chromium.org>
Reviewed-by: Alex Klein <saklein@chromium.org>
Commit-Queue: Alex Klein <saklein@chromium.org>

repo_launcher

@@ -149,7 +149,7 @@ if not REPO_REV:
 BUG_URL = 'https://bugs.chromium.org/p/gerrit/issues/entry?template=Repo+tool+issue'
 
 # increment this whenever we make important changes to this script
-VERSION = (2, 17)
+VERSION = (2, 21)
 
 # increment this if the MAINTAINER_KEYS block is modified
 KEYRING_VERSION = (2, 3)
@@ -372,7 +372,7 @@ def InitParser(parser, gitc_init=False):
                    help='filter for use with --partial-clone '
                         '[default: %default]')
   group.add_option('--use-superproject', action='store_true', default=None,
-                   help='use the manifest superproject to sync projects')
+                   help='use the manifest superproject to sync projects; implies -c')
   group.add_option('--no-use-superproject', action='store_false',
                    dest='use_superproject',
                    help='disable use of manifest superprojects')
@@ -382,6 +382,11 @@ def InitParser(parser, gitc_init=False):
   group.add_option('--no-clone-bundle',
                    dest='clone_bundle', action='store_false',
                    help='disable use of /clone.bundle on HTTP/HTTPS (default if --partial-clone)')
+  group.add_option('--git-lfs', action='store_true',
+                   help='enable Git LFS support')
+  group.add_option('--no-git-lfs',
+                   dest='git_lfs', action='store_false',
+                   help='disable Git LFS support')
 
   # Tool.
   group = parser.add_option_group('repo Version options')
@@ -618,6 +623,7 @@ def _Init(args, gitc_init=False):
             "REPO_URL set correctly?" % url, file=sys.stderr)
 
   except CloneFailure:
+    print('fatal: double check your --repo-rev setting.', file=sys.stderr)
     if opt.quiet:
       print('fatal: repo init failed; run without --quiet to see why',
             file=sys.stderr)