Silence git-hooks/pre-commit in the absence of .gitmodules.

Silence git-hooks/pre-commit in the absence of .gitmodules.

Other projects use depot_tools (which pulls in this hook) and chromium's build/
(where the hook lives) but don't use git modules (e.g. webrtc).

[Ami GONE FROM CHROMIUM, 2014-03-10 19:04:48]

@szager: PTAL.

https://codereview.chromium.org/192833005/diff/20001/git-hooks/pre-commit
File git-hooks/pre-commit (right):

https://codereview.chromium.org/192833005/diff/20001/git-hooks/pre-commit#new...
git-hooks/pre-commit:26: if [[ -n "$(git ls-files .gitmodules)" &&
Sample noise that this silences:
fatal: ambiguous argument '.gitmodules': unknown revision or path not in the
working tree.
Use '--' to separate paths from revisions, like this:
'git <command> [<revision>...] -- [<file>...]'

FWIW I replaced "test" with "[[" b/c [[ short-circuits evaluation while test
does not (so keeping "test" would require a nested:
if test -n "$(..ls-files..)"; then
  if test -n "$(..diff-index..)"; then
The [[ form seems clearer to me but I don't really care.

[Ami GONE FROM CHROMIUM, 2014-03-17 03:49:16]

szager: ping?

[szager1, 2014-03-17 04:17:27]

Sorry for the delay

lgtm, thanks

[Ami GONE FROM CHROMIUM, 2014-03-17 04:18:19]

The CQ bit was checked by fischman@chromium.org

[commit-bot: I haz the power, 2014-03-17 04:18:26]

CQ is trying da patch. Follow status at
https://chromium-status.appspot.com/cq/fischman@chromium.org/192833005/20001

[commit-bot: I haz the power, 2014-03-17 04:22:41]

The CQ bit was unchecked by commit-bot@chromium.org

[commit-bot: I haz the power, 2014-03-17 04:22:42]

Try jobs failed on following builders:
  tryserver.chromium on mac_chromium_rel

[Ami GONE FROM CHROMIUM, 2014-03-17 16:37:58]

Base URL for this issue was busted (b/c uploaded from a non-chromium checkout). 
Closing this in favor of https://codereview.chromium.org/196413021.