bug#36644: Git log search

[Eli Zaretskii]

> From: Robert Pluim <rpluim@gmail.com>
> Cc: Eli Zaretskii <eliz@gnu.org>,  "36644\@debbugs.gnu.org"
>  <36644@debbugs.gnu.org>,  Juri Linkov <juri@linkov.net>
> Date: Wed, 24 Jul 2019 18:13:53 +0200
> 
> "Search a log of changes for PATTERN.
> 
> How PATTERN is interpreted will depend on how each individual
> backend's log search command is implemented, as some can only match
> fixed strings, some have regular expression support, etc."

I think this should also mention that most backends will interpret
PATTERN as a regular expression.  Something like this:

    "Search the log of changes for PATTERN.

  PATTERN is usually interpreted as a regular expression.  However, its
  exact semantics is up to the backend's log search command; some can
  only match fixed strings."