>> > Stepping a notch back, wasn't the original request to have a command
>> > that would display a specific commit?  If so, that's not a "log"
>> > command, that's closer to a "diff" command.  And don't we already have
>> > a "diff" command which shows diffs for a specific revision?
>>
>> Then we could use something like the existing backend 'region-history'
>> that for vc-git uses 'git log', but displays both the log and diff
>> in one output buffer.
>
> region-history is slow, so I'm not sure it is a good starting point
> for this feature.  A diff command is usually very fats with every VCS.

It doesn't use 'region-history'.  I meant using 'region-history-mode'
on the output buffer.  Everything works perfectly with this patch
that also implements defaulting to the revision under point and
prompting for the directory like Lars asked to do: