git-gc: run pack-refs by default unless the repo is bare

The config variable gc.packrefs is tristate now: "true", "false"
and "notbare", where "notbare" is the default.

Signed-off-by: Johannes Schindelin <Johannes.Schindelin@gmx.de>
Signed-off-by: Junio C Hamano <junkio@cox.net>

Documentation/config.txt

@@ -321,6 +321,17 @@ format.headers::
 	Additional email headers to include in a patch to be submitted
 	by mail.  See gitlink:git-format-patch[1].
 
+gc.packrefs::
+	`git gc` does not run `git pack-refs` in a bare repository by
+	default so that older dumb-transport clients can still fetch
+	from the repository.  Setting this to `true` lets `git
+	gc` to run `git pack-refs`.  Setting this to `false` tells
+	`git gc` never to run `git pack-refs`. The default setting is
+	`notbare`. Enable it only when you know you do not have to
+	support such clients.  The default setting will change to `true`
+	at some stage, and setting this to `false` will continue to
+	prevent `git pack-refs` from being run from `git gc`.
+
 gc.reflogexpire::
 	`git reflog expire` removes reflog entries older than
 	this time; defaults to 90 days.

Documentation/git-gc.txt

@@ -62,6 +62,10 @@ The optional configuration variable 'gc.rerereunresolved' indicates
 how long records of conflicted merge you have not resolved are
 kept.  This defaults to 15 days.
 
+The optional configuration variable 'gc.packrefs' determines if
+`git gc` runs `git-pack-refs`.  Without the configuration, `git-pack-refs`
+is not run in bare repositories by default, to allow older dumb-transport
+clients fetch from the repository,  but this will change in the future.
 
 See Also
 --------

git-gc.sh

@@ -22,6 +22,14 @@ do
 	shift
 done
 
+case "$(git config --get gc.packrefs)" in
+notbare|"")
+	test $(is_bare_repository) = true || pack_refs=true;;
+*)
+	pack_refs=$(git config --bool --get gc.packrefs)
+esac
+
+test "true" != "$pack_refs" ||
 git-pack-refs --prune &&
 git-reflog expire --all &&
 git-repack -a -d -l &&