We use CommitFilesController also for the files of commits that we show
elsewhere, e.g. for branch commits, tags, or stashes. It doesn't make sense to
discard changes from those (for stashes it might be possible to implement it
somehow, but that would be a new feature), so we disallow it unless we are in
the local commits panel.
Discarding changes to an entire directory doesn't quite work correctly in all
cases; for example, if the current commit added files to the directory (but the
directory existed before) then those files won't be removed.
It might be possible to fix the command so that these cases always work for
directories, but I don't think it's worth the effort (you can always use a
custom patch for that), so let's display an error for now.
We have not been good at consistent casing so far. Now we use 'Sentence case' everywhere. EVERYWHERE.
Also Removing 'Lc' prefix from i18n field names: the 'Lc' stood for lowercase but now that everything
is in 'Sentence case' there's no need for the distinction.
I've got a couple lower case things I've kept: namely, things that show up in parentheses.
