git-[short]log.txt: unify quoted standalone --

In git-log.txt, we have an instance of \--, which is known to sometimes
render badly. This one is even worse than normal though, since ``\-- ''
(with or without that trailing space) appears to be entirely broken,
both in HTML and manpages, both with AsciiDoc (version 8.6.9) and
Asciidoctor (version 1.5.4).

Further down in git-log.txt we have a ``--'', which renders good. In
git-shortlog.txt, we use "\-- " (including the quotes and the space),
which happens to look fairly good. I failed to find any other similar
instances. So all in all, we quote a double-dash in three different
places and do it differently each time, with various degrees of success.

Switch all of these to `--`. This sets the double-dash in monospace and
matches what we usually do with example command line usages and options.
Note that we drop the trailing space as well, since `-- ` does not
render well. These should still be clear enough since just a few lines
above each instance, the space is clearly visible in a longer context.

Signed-off-by: Martin Ågren <[email protected]>

Author: Martin Ågren

Documentation/git-log.txt

@@ -96,7 +96,7 @@ include::line-range-format.txt[]
 	Simplification' below for details and other simplification
 	modes.
 +
-Paths may need to be prefixed with ``\-- '' to separate them from
+Paths may need to be prefixed with `--` to separate them from
 options or the revision range, when confusion arises.
 
 include::rev-list-options.txt[]
@@ -125,7 +125,7 @@ EXAMPLES
 `git log --since="2 weeks ago" -- gitk`::
 
 	Show the changes during the last two weeks to the file 'gitk'.
-	The ``--'' is necessary to avoid confusion with the *branch* named
+	The `--` is necessary to avoid confusion with the *branch* named
 	'gitk'
 
 `git log --name-status release..test`::

Documentation/git-shortlog.txt

@@ -73,7 +73,7 @@ them.
 	Consider only commits that are enough to explain how the files
 	that match the specified paths came to be.
 +
-Paths may need to be prefixed with "\-- " to separate them from
+Paths may need to be prefixed with `--` to separate them from
 options or the revision range, when confusion arises.
 
 MAPPING AUTHORS