Add --sync option, to only sync submodules.

git-crup

 #!/bin/bash
 # Copyright (c) 2012 The Chromium Authors. All rights reserved.
 # Use of this source code is governed by a BSD-style license that can be
 # found in the LICENSE file.
 
 # A convenience script to largely replicate the behavior of `gclient sync` in a
 # submodule-based checkout.  Fetches latest commits for top-level solutions;
 # updates submodules; and runs post-sync hooks.
 
 # Auto-update depot_tools
@@ skipping 27 matching lines @@
 fi
 
 if ( echo test | xargs -I bar true 2>/dev/null ); then
   replace_arg="-I replace_arg"
 else
   replace_arg="-ireplace_arg"
 fi
 
 usage() {
   cat <<EOF
-Usage: git-crup [-n|--dry-run] [--fetch] [-j|--jobs [jobs]]
+Usage: git-crup [-n|--dry-run] [--fetch|--sync] [-j|--jobs [jobs]]
     [--no-hooks] [<args to git-pull or git-fetch>]
 EOF
 }
 
 serial_update() {
   ( cd "$1"
-    $GIT_EXE $pull $pull_args -q origin | sed "s/^/[$1] /g"
-    if [ $? -ne 0 ]; then
-      return $?
+    if test -n "$toplevel_cmd"; then
+      $toplevel_cmd | sed "s/^/[$1] /g"
+      if [ $? -ne 0 ]; then
+        return $?
+      fi
     fi
     $GIT_EXE submodule --quiet sync
     $GIT_EXE ls-files -s | grep ^160000 | awk '{print $4}' |
     while read submod; do
       "$crup_runner" "$1/$submod"
     done
   )
 }
 
 while test $# -ne 0; do
@@ skipping 18 matching lines @@
     -n|--dry-run)
       ECHO=echo
       ;;
     -h|--help)
       usage
       exit 0
       ;;
     --fetch)
       pull=fetch
       ;;
+    --sync)
+      pull=
+      ;;
     --no-hooks|--nohooks)
       hooks=no
       ;;
     *)
       pull_args="$pull_args $1"
       break
       ;;
   esac
   shift
 done
@@ skipping 11 matching lines @@
 
 if ( echo test test | xargs -P 2 true 2>/dev/null ); then
   xargs_parallel=yes
 else
   if test "$j" != "1"; then
     echo "Warning: parallel execution is not supported on this platform." 1>&2
   fi
   xargs_parallel=no
 fi
 
+if test -n "$pull"; then
+  toplevel_cmd="$GIT_EXE $pull $pull_args -q origin"
+else
+  toplevel_cmd=
+fi
+
 set -o pipefail
 if test "$xargs_parallel" = "yes"; then
   ( ls -d */.git | sed 's/\/\.git$//' |
    xargs $max_lines $replace_arg -P "$j" \
-      "$crup_runner" replace_arg $GIT_EXE $pull $pull_args -q origin |
+      "$crup_runner" replace_arg $toplevel_cmd |
    xargs $max_lines -P "$j" "$crup_runner" )
 else 
   ls -d */.git |
   while read gitdir; do
     serial_update "${gitdir%%/.git}"
   done
 fi
 
 status=$?
 
 if [ "$status" -ne 0 ]; then
   cat 1>&2 <<EOF
 Please check the preceding terminal output for error messages.
 Run 'git submodule status' to see the current state of submodule checkouts.
 EOF
   exit $status
 fi
 
 if [ "$hooks" = "yes" ]; then
   "$runhooks"
   status=$?
 fi
 
 echo
 exit $status