Restrict tag-update for version generation to cached git repos.

Restrict tag-update for version generation to cached git repos.

Otherwise it's impossible to compile v8 without internet
connection.

BUG=chromium:446166
LOG=n
NOTRY=true

Committed: https://crrev.com/c6641e138bb4a81b47f70e62bb9113c87b590a6f
Cr-Commit-Position: refs/heads/master@{#26186}

[Jakob Kummerow, 2015-01-21 10:02:09]

jkummerow@chromium.org changed reviewers:
+ jkummerow@chromium.org

[Jakob Kummerow, 2015-01-21 10:02:10]

lgtm

[Michael Achenbach, 2015-01-21 10:07:39]

machenbach@chromium.org changed reviewers:
+ jochen@chromium.org, tandrii@chromium.org

[Michael Achenbach, 2015-01-21 10:08:20]

The CQ bit was checked by machenbach@chromium.org

[commit-bot: I haz the power, 2015-01-21 10:08:40]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/856323002/1

[commit-bot: I haz the power, 2015-01-21 11:15:47]

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

[commit-bot: I haz the power, 2015-01-21 11:15:48]

Try jobs failed on following builders:
  v8_linux_arm_rel on tryserver.v8
(http://build.chromium.org/p/tryserver.v8/builders/v8_linux_arm_rel/builds/823)

[Michael Achenbach, 2015-01-21 11:16:52]

The CQ bit was checked by machenbach@chromium.org

[commit-bot: I haz the power, 2015-01-21 11:17:14]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/856323002/1

[commit-bot: I haz the power, 2015-01-21 12:07:29]

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

[commit-bot: I haz the power, 2015-01-21 12:07:31]

Try jobs failed on following builders:
  v8_linux_arm_rel on tryserver.v8
(http://build.chromium.org/p/tryserver.v8/builders/v8_linux_arm_rel/builds/832)

[Michael Achenbach, 2015-01-21 12:37:34]

The CQ bit was checked by machenbach@chromium.org

[commit-bot: I haz the power, 2015-01-21 12:38:25]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/856323002/1

[commit-bot: I haz the power, 2015-01-21 13:02:31]

Committed patchset #1 (id:1)

[commit-bot: I haz the power, 2015-01-21 13:02:45]

Patchset 1 (id:??) landed as
https://crrev.com/c6641e138bb4a81b47f70e62bb9113c87b590a6f
Cr-Commit-Position: refs/heads/master@{#26186}