Support log.follow automatically

[duncanmak]

tig has the --follow option (#361), but since Git 2.9, there's a git config option called log.follow.

log.follow

If true, git log will act as if the --follow option was used when a single <path> is 
given. This has the same limitations as --follow, i.e. it cannot be used to follow 
multiple files and does not work well on non-linear history.

If this is turned on, tig gets a bit confused, and the commits start veering off to the right.

It would be great if --follow can be turned on automatically if log.follow is enabled.

I'm running tig version 2.4.1 on OS X.

[duncanmak]

Thanks @jonas!

With this change, what happens if log.follow is enabled?