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

[Juri Linkov]

>> Making the choice whether the word is hexinumeric doesn't look too
>> unambiguous.  What if the user wants to search a hexinumeric word
>> in the text of commit messages?  For example, searching for "5761a1a393"
>> to find messages that contain "Revert commit 5761a1a393 ..."
>
> Then they would call one of the non-dwim commands.

Then no dwim command is needed.  We'll just add vc-log-revision and done.
The user will decide whether to use vc-log-search to search in commit
messages, or vc-log-revision to show the log message of one commit.

If adding a new command is not desirable, then add a prefix to existing.
'C-x v L' already uses a prefix arg to prompt for LIMIT, that can be 1.
Another prefix arg could ask for a revision, e.g. 'C-u C-u C-x L 5761a1a393'.