Revert of bot_update: fix git dir check

Revert of bot_update: fix git dir check (patchset #1 id:1 of https://codereview.chromium.org/2174923002/ )

Reason for revert:
this is wrong. if directory is not empty, git clone fails

Original issue's description:
> bot_update: fix git dir check
> 
> existance of a dir does not mean it is a git repo. Check .git dir
> presence instead.
> 
> This is the reason why swarmbucket build.git builds fail.
> 
> TBR=hinoka@chromium.org
> BUG=
> 
> Committed: https://chromium.googlesource.com/chromium/tools/depot_tools/+/cdac80c9fb4768bdc5bc42734e852e1f216224c9

TBR=hinoka@chromium.org
# Skipping CQ checks because original CL landed less than 1 days ago.
NOPRESUBMIT=true
NOTREECHECKS=true
NOTRY=true
BUG=

Committed: https://chromium.googlesource.com/chromium/tools/depot_tools/+/b96f2d5b1dd025c4392bc9b41a95d75e749e04d0

[nodir, 2016-07-22 22:48:59]

The CQ bit was checked by nodir@chromium.org

[nodir, 2016-07-22 22:49:00]

Created Revert of bot_update: fix git dir check

[commit-bot: I haz the power, 2016-07-22 22:49:06]

CQ is trying da patch. Follow status at
 
https://chromium-cq-status.appspot.com/v2/patch-status/codereview.chromium.or...

[commit-bot: I haz the power, 2016-07-22 22:49:13]

Description was changed from

==========
Revert of bot_update: fix git dir check (patchset #1 id:1 of
https://codereview.chromium.org/2174923002/ )

Reason for revert:
this is wrong. if directory is not empty, git clone fails

Original issue's description:
> bot_update: fix git dir check
> 
> existance of a dir does not mean it is a git repo. Check .git dir
> presence instead.
> 
> This is the reason why swarmbucket build.git builds fail.
> 
> TBR=hinoka@chromium.org
> BUG=
> 
> Committed:
https://chromium.googlesource.com/chromium/tools/depot_tools/+/cdac80c9fb4768...

TBR=hinoka@chromium.org
# Skipping CQ checks because original CL landed less than 1 days ago.
NOPRESUBMIT=true
NOTREECHECKS=true
NOTRY=true
BUG=
==========

to

==========
Revert of bot_update: fix git dir check (patchset #1 id:1 of
https://codereview.chromium.org/2174923002/ )

Reason for revert:
this is wrong. if directory is not empty, git clone fails

Original issue's description:
> bot_update: fix git dir check
> 
> existance of a dir does not mean it is a git repo. Check .git dir
> presence instead.
> 
> This is the reason why swarmbucket build.git builds fail.
> 
> TBR=hinoka@chromium.org
> BUG=
> 
> Committed:
https://chromium.googlesource.com/chromium/tools/depot_tools/+/cdac80c9fb4768...

TBR=hinoka@chromium.org
# Skipping CQ checks because original CL landed less than 1 days ago.
NOPRESUBMIT=true
NOTREECHECKS=true
NOTRY=true
BUG=

Committed:
https://chromium.googlesource.com/chromium/tools/depot_tools/+/b96f2d5b1dd025...
==========

[commit-bot: I haz the power, 2016-07-22 22:49:14]

Committed patchset #1 (id:1) as
https://chromium.googlesource.com/chromium/tools/depot_tools/+/b96f2d5b1dd025...