install latest git to support version sorting

[koenpunt]

Followup on #2527

This enables docker based builds, and updates Git to the latest stable version, to support sorting based on version instead of alphabetically.

[koenpunt]

But I now see that using Docker doesn't really result in faster build times.. While testing it turns out that with the git install the build time is the same on both stacks. But the container stack has a shorter wait time until it's starting.

For reference;

Precise: https://travis-ci.org/harvesthq/chosen/builds/107869514
Container: https://travis-ci.org/harvesthq/chosen/builds/107867054

[tjschuck]

I'm pretty sure it can just be git by itself and not reference git-core anymore. git-core was a transitional name because of goofy reasons — it should now just be a dummy package that points to git as its only dependency.

[koenpunt]

git-core is the only one on the whitelist, so maybe it's true for regular apt, but not with the docker addons.

[koenpunt]

And these are sources, not packages, the package is simply git

[tjschuck]

Interesting. It looks like that whitelist entry was only added 18 days ago in travis-ci/apt-source-safelist#225. This is fine with me then, because I don't feel like PR'ing the addition of git to the whitelist 😜

[pfiller]

Coooooooooool with me. Thanks @koenpunt!