If a nameless buffer with changes is opened, fail gracefully

[ibizaman]

For now, if a nameless buffer with changes is opened while using promiscuous, it will create a [Promiscuous] commit but will fail when trying to close the aforementioned buffer, leaving us in an intermediate state where 1/ we lost the vim buffer windows and tabs layout 2/ we have an unwanted commit.

A check to see if such a buffer should be made prior to changing the current vim and git state.

[lourenci]

I think it happens even with named buffers, the buffer just hasn't been saved.

What if we :noautocmd bufdo update?