Re: Merge-base alias for git vc-diff

[Juri Linkov]

> 2. A diff is always a comparison of two revisions, right?  For vc-dir,
>    isn't a UI like query-replace's suitable here?  You know, that thing
>    where you type the pattern and the replacement interactively in the
>    same minibuffer prompt, separated by the arrow.  You can M-p, C-r,
>    etc, flawlessly. I really like that UI, it's really intuitive (kudos
>    to whoever participated, btw).
>
>    So here, instead of pattern and replacement, two revisions.  All one
>    would need, apparently, is to turn the arrow into a ".." and make it
>    toggleable to "..." with say, C-M-y.  I think it would simplify the
>    completion problem: on both sides of the ".." or "..." you just
>    complete a revision using whatever system we presumably already have
>    in place for that.

Good idea.  This brings the minibuffer input syntax closer to the real
command line syntax.  The only problem is that then we have to use
different amount of dots for vc-root-diff and vc-print-root-log because
in git: ‘git diff A...B’ corresponds to ‘git log A..B’
whereas ‘git diff A..B’ corresponds to ‘git log A...B’