bug#38044: 27.0.50; There should be an easier way to look at a specific vc commit

[Juri Linkov]

>>> For that case, Emacs should have a command that prompts for an ID
>>> (defaulting to the ID under point), and then (unless default-directory
>>> is already in a vc-controlled directory), prompts for the directory to
>>> look for that ID, and then display the commit.
>>
>> I wrote such a command (appended below) for my own use, but it's
>> git-specific and I don't know the innards of VC well enough to adapt it,
>> which is why I haven't proposed it for inclusion in Emacs.  Maybe some
>> of it could be used for a VC command.
>
> It should be easy to add a command properly integrated into the innards of VC
> by just grepping for "log-search" in lisp/vc/vc*.el (there are only 7 
> matches),
> and after copying to replace "log-search" with "log-show", and the new command
> is ready.

Actually "log-show" is a bad name.  It's too git-specific OT1H,
and OTOH it's too general since its output varies that doesn't fit
to log-view-mode.

I hoped git would be able to search both sha and commit message
in one command, something like:

  git log -1 5761a1a393 --grep=5761a1a393

to output the log of sha 5761a1a393, and logs of matching commit messages,
but this is not possible in git.