[Qgit RFC] commit --amend

Hello,

I am thinking about adding commit --amend support to Qgit.

However I see three ways to do it, so I'd like to ask whether anybody knows some reason why any of them is better or worse, which I don't:

 - Add a button for "Amend". This would fit with what is there currently,
   because with stgit it has buttons "New patch" and "Add to top" (refresh),
   which correspond exactly to core git's "commit" and "commit --amend"
   respectively.

   Disadvantage (for current approach too) is, that when amending (resp.
   refreshing) the previous commit message is not there to be edited.

 - Add a radio button the way git-gui does. Switching the button to "amend"
   would load the previous commit message.

   This would be more invasive change, but it would allow editing the commit
   message when amending/refreshing. I fear it will be more user-error-prone
   too, though.

 - Add a separate action to the menu. This action would take over the refresh
   (Add to top) operation when using stgit.
   
   I believe this has lower risk of user errors than the previous option. It
   also has the advantage, that I don't have to touch the disabling logic for
   the commit action. Amending last commit is always possible, even if there
   are no changes, because you might want to edit the message (eg. if you
   forget to sign-off or forget to mention some change or something).

I'll try doing the first option now, unless somebody persuades me that it's a nonsense.