[PATCH v3 3/6] for-each-ref: introduce %(HEAD) asterisk marker

[Ramkumar Ramachandra <artagnon@gmail.com>]

'git branch' shows which branch you are currently on with an '*', but
'git for-each-ref' misses this feature.  So, extend its format with
%(HEAD) for the same effect.

Now you can use the following format in for-each-ref:

  %(HEAD) %(refname:short)

to display an asterisk next to the current ref.

Signed-off-by: Ramkumar Ramachandra <artagnon@gmail.com>
---
 Documentation/git-for-each-ref.txt |  4 ++++
 builtin/for-each-ref.c             | 13 +++++++++++--
 t/t6300-for-each-ref.sh            |  2 ++
 3 files changed, 17 insertions(+), 2 deletions(-)

diff --git a/Documentation/git-for-each-ref.txt b/Documentation/git-for-each-ref.txt
index f2e08d1..ab3da0e 100644
--- a/Documentation/git-for-each-ref.txt
+++ b/Documentation/git-for-each-ref.txt
@@ -93,6 +93,10 @@ upstream::
 	from the displayed ref. Respects `:short` in the same way as
 	`refname` above.
 
+HEAD::
+	Used to indicate the currently checked out branch.  Is '*' if
+	HEAD points to the current ref, and ' ' otherwise.
+
 In addition to the above, for commit and tag objects, the header
 field names (`tree`, `parent`, `object`, `type`, and `tag`) can
 be used to specify the value in the header field.
diff --git a/builtin/for-each-ref.c b/builtin/for-each-ref.c
index 1d4083c..5f1842f 100644
--- a/builtin/for-each-ref.c
+++ b/builtin/for-each-ref.c
@@ -75,6 +75,7 @@ static struct {
 	{ "upstream" },
 	{ "symref" },
 	{ "flag" },
+	{ "HEAD" },
 };
 
 /*
@@ -675,8 +676,16 @@ static void populate_value(struct refinfo *ref)
 				v->s = xstrdup(buf + 1);
 			}
 			continue;
-		}
-		else
+		} else if (!strcmp(name, "HEAD")) {
+			const char *head;
+			unsigned char sha1[20];
+			head = resolve_ref_unsafe("HEAD", sha1, 1, NULL);
+			if (!strcmp(ref->refname, head))
+				v->s = "*";
+			else
+				v->s = " ";
+			continue;
+		} else
 			continue;
 
 		formatp = strchr(name, ':');
diff --git a/t/t6300-for-each-ref.sh b/t/t6300-for-each-ref.sh
index e1f71ff..5e29ffc 100755
--- a/t/t6300-for-each-ref.sh
+++ b/t/t6300-for-each-ref.sh
@@ -77,6 +77,7 @@ test_atom head contents:body ''
 test_atom head contents:signature ''
 test_atom head contents 'Initial
 '
+test_atom head HEAD '*'
 
 test_atom tag refname refs/tags/testtag
 test_atom tag upstream ''
@@ -110,6 +111,7 @@ test_atom tag contents:body ''
 test_atom tag contents:signature ''
 test_atom tag contents 'Tagging at 1151939927
 '
+test_atom tag HEAD ' '
 
 test_expect_success 'Check invalid atoms names are errors' '
 	test_must_fail git for-each-ref --format="%(INVALID)" refs/heads
-- 
1.8.5.rc0.6.gfd75b41