This change makes it actually possible to get around commit-time out-of-dateness by running 'got update'. The test added with this commit shows that our out-of-dateness check is currently too simplistic; an update is required between any two commit operations! It would be better to allow commits to proceed until a situation arises where file content must be merged.

bails on empty messages, trims leading and trailing newlines this currently disables the unveil in the commit process because it's not compatible with spawning the editor also prevent commits when there are no changes

$> got rm a got: : No such file or directory becomes $> got rm a got: /path/to/a: No such file or directory