Document gc.<pattern>.reflogexpire variables

3cb22b8 (Per-ref reflog expiry configuration, 2008-06-15) added support
for setting the expiry parameters differently for different reflog, but
it was never documented.

Signed-off-by: Junio C Hamano <gitster@pobox.com>

Documentation/config.txt

@@ -885,13 +885,19 @@ gc.pruneexpire::
 	unreachable objects immediately.
 
 gc.reflogexpire::
+gc.<pattern>.reflogexpire::
 	'git-reflog expire' removes reflog entries older than
-	this time; defaults to 90 days.
+	this time; defaults to 90 days.  With "<pattern>" (e.g.
+	"refs/stash") in the middle the setting applies only to
+	the refs that match the <pattern>.
 
 gc.reflogexpireunreachable::
+gc.<ref>.reflogexpireunreachable::
 	'git-reflog expire' removes reflog entries older than
 	this time and are not reachable from the current tip;
-	defaults to 30 days.
+	defaults to 30 days.  With "<pattern>" (e.g. "refs/stash")
+	in the middle, the setting applies only to the refs that
+	match the <pattern>.
 
 gc.rerereresolved::
 	Records of conflicted merge you resolved earlier are

Documentation/git-gc.txt

@@ -88,6 +88,16 @@ commits prior to the amend or rebase occurring.  Since these changes
 are not part of the current project most users will want to expire
 them sooner.  This option defaults to '30 days'.
 
+The above two configuration variables can be given to a pattern.  For
+example, this sets non-default expiry values only to remote tracking
+branches:
+
+------------
+[gc "refs/remotes/*"]
+	reflogExpire = never
+	reflogexpireUnreachable = 3 days
+------------
+
 The optional configuration variable 'gc.rerereresolved' indicates
 how long records of conflicted merge you resolved earlier are
 kept.  This defaults to 60 days.