git-svn: document useLogAuthor and addAuthorFrom config keys

We've always supported these config keys in git-svn,
so document them so users won't have to respecify them
on every invocation.

Reported-by: Juergen Kosel <juergen.kosel@gmx.de>
Signed-off-by: Eric Wong <e@80x24.org>

Documentation/git-svn.txt

@@ -664,13 +664,19 @@ creating the branch or tag.
 	When retrieving svn commits into Git (as part of 'fetch', 'rebase', or
 	'dcommit' operations), look for the first `From:` or `Signed-off-by:` line
 	in the log message and use that as the author string.
++
+[verse]
+config key: svn.useLogAuthor
+
 --add-author-from::
 	When committing to svn from Git (as part of 'commit-diff', 'set-tree' or 'dcommit'
 	operations), if the existing log message doesn't already have a
 	`From:` or `Signed-off-by:` line, append a `From:` line based on the
 	Git commit's author string.  If you use this, then `--use-log-author`
 	will retrieve a valid author string for all commits.
-
++
+[verse]
+config key: svn.addAuthorFrom
 
 ADVANCED OPTIONS
 ----------------