builtin-remote: add set-head subcommand

Provide a porcelain command for setting and deleting
$GIT_DIR/remotes/<remote>/HEAD.

While we're at it, document what $GIT_DIR/remotes/<remote>/HEAD is all
about.

Signed-off-by: Jay Soffian <jaysoffian@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

1 files changed, 40 insertions, 0 deletions

diff --git a/t/t5505-remote.sh b/t/t5505-remote.sh
index 91525c3f9..de1d0fcf4 100755
--- a/t/t5505-remote.sh
+++ b/t/t5505-remote.sh
@@ -205,6 +205,46 @@ test_expect_success 'prune' '
 	 test_must_fail git rev-parse refs/remotes/origin/side)
 '
 
+test_expect_success 'set-head --delete' '
+	(cd test &&
+	 git symbolic-ref refs/remotes/origin/HEAD &&
+	 git remote set-head --delete origin &&
+	 test_must_fail git symbolic-ref refs/remotes/origin/HEAD)
+'
+
+test_expect_success 'set-head --auto' '
+	(cd test &&
+	 git remote set-head --auto origin &&
+	 echo refs/remotes/origin/master >expect &&
+	 git symbolic-ref refs/remotes/origin/HEAD >output &&
+	 test_cmp expect output
+	)
+'
+
+cat >test/expect <<EOF
+error: Multiple remote HEAD branches. Please choose one explicitly with:
+  git remote set-head two another
+  git remote set-head two master
+EOF
+
+test_expect_success 'set-head --auto fails w/multiple HEADs' '
+	(cd test &&
+	 test_must_fail git remote set-head --auto two >output 2>&1 &&
+	test_cmp expect output)
+'
+
+cat >test/expect <<EOF
+refs/remotes/origin/side2
+EOF
+
+test_expect_success 'set-head explicit' '
+	(cd test &&
+	 git remote set-head origin side2 &&
+	 git symbolic-ref refs/remotes/origin/HEAD >output &&
+	 git remote set-head origin master &&
+	 test_cmp expect output)
+'
+
 cat > test/expect << EOF
 Pruning origin
 URL: $(pwd)/one