bug#36644: Git log search

[Juri Linkov]

>     >>> Git supports regexps, but maybe we should look at what other backends
>     >>> can support as well.
>     >>
>     >> It seems the most compatible type is string.
>
>     Dmitry> OK, if that is your conclusion.
>
> If the most compatible type is string, surely emacs should do no
> regexp-quoting or anything else on the argument, but just pass it
> verbatim to the backend search command. That way you could do eg
>
> Bug.*0
>
> to get all log entries with a bug reference ending in 0.

Currently when using shell-quote-argument it doesn't allow
using such regexps as Bug.*0.  So I guess we need to remove
shell-quote-argument and also to not use regexp-quote.