revision walker: include a detached HEAD in --all

When HEAD is detached, --all should list it, too, logically, as a
detached HEAD is by definition a temporary, unnamed branch.

It is especially necessary to list it when garbage collecting, as
the detached HEAD would be trashed.

Noticed by Thomas Rast.

Note that this affects creating bundles with --all; I contend that it
is a good change to add the HEAD, so that cloning from such a bundle
will give you a current branch.  However, I had to fix t5701 as it
assumed that --all does not imply HEAD.

Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

revision.c

@@ -1223,6 +1223,7 @@ int setup_revisions(int argc, const char **argv, struct rev_info *revs, const ch
 
 			if (!strcmp(arg, "--all")) {
 				handle_refs(revs, flags, for_each_ref);
+				handle_refs(revs, flags, head_ref);
 				continue;
 			}
 			if (!strcmp(arg, "--branches")) {

t/t5701-clone-local.sh

@@ -11,8 +11,8 @@ test_expect_success 'preparing origin repository' '
 	git clone --bare . x &&
 	test "$(GIT_CONFIG=a.git/config git config --bool core.bare)" = true &&
 	test "$(GIT_CONFIG=x/config git config --bool core.bare)" = true
-	git bundle create b1.bundle --all HEAD &&
-	git bundle create b2.bundle --all &&
+	git bundle create b1.bundle master HEAD &&
+	git bundle create b2.bundle master &&
 	mkdir dir &&
 	cp b1.bundle dir/b3
 	cp b1.bundle b4

t/t6014-rev-list-all.sh

@@ -0,0 +1,38 @@
+#!/bin/sh
+
+test_description='--all includes detached HEADs'
+
+. ./test-lib.sh
+
+
+commit () {
+	test_tick &&
+	echo $1 > foo &&
+	git add foo &&
+	git commit -m "$1"
+}
+
+test_expect_success 'setup' '
+
+	commit one &&
+	commit two &&
+	git checkout HEAD^ &&
+	commit detached
+
+'
+
+test_expect_success 'rev-list --all lists detached HEAD' '
+
+	test 3 = $(git rev-list --all | wc -l)
+
+'
+
+test_expect_success 'repack does not lose detached HEAD' '
+
+	git gc &&
+	git prune --expire=now &&
+	git show HEAD
+
+'
+
+test_done