Let git checkout on buildbots retry on failure.

[pulkomandy]

We have rather frequent failures on our bots similar to this: ​http://buildbot.haiku-os.org/builders/haiku-master-x86_hybrid/builds/1572 The build fails while checking out the source.

This is rather annoying as it is hard to detect actual build failures in these conditions (and it spams the IRC channel with failure then success notifications).

According to ​http://docs.buildbot.net/latest/manual/cfg-buildsteps.html the checkout step can have a retry parameter:

retry If set, this specifies a tuple of (delay, repeats) which means that when a full VC checkout fails, it should be retried up to repeats times, waiting delay seconds between attempts. If you don't provide this, it defaults to None, which means VC operations should not be retried. This is provided to make life easier for buildslaves which are stuck behind poor network connections.

We should enable this, so these temporary failures are not too annoying.

[zooey]

All our Git steps use the following:

• retry = (30, 10)
• retryFetch = True

Unfortunately, this does not seem to help.

[pulkomandy]

Ok, in that particular case there was a config problem on the buildslave (firewalld/iptables was interfering with git). The slave has been fixed.