[RFC/PATCH 02/11] ref-filter: add 'colornext' atom

[Karthik Nayak <karthik.188@gmail.com>]

The 'colornext' atom allows us to color only the succeeding atom with
a particular color. This resets any previous color preferences set. It
is not compatible with `padright`. This is required for printing
formats like `git branch -vv` where the upstream is colored in blue.

Mentored-by: Christian Couder <christian.couder@gmail.com>
Mentored-by: Matthieu Moy <matthieu.moy@grenoble-inp.fr>
Signed-off-by: Karthik Nayak <karthik.188@gmail.com>
---
 Documentation/git-for-each-ref.txt |  5 +++++
 ref-filter.c                       | 20 +++++++++++++++++++-
 ref-filter.h                       |  4 +++-
 t/t6302-for-each-ref-filter.sh     | 16 ++++++++++++++++
 4 files changed, 43 insertions(+), 2 deletions(-)

diff --git a/Documentation/git-for-each-ref.txt b/Documentation/git-for-each-ref.txt
index 2b60aee..9dc02aa 100644
--- a/Documentation/git-for-each-ref.txt
+++ b/Documentation/git-for-each-ref.txt
@@ -133,6 +133,11 @@ padright::
 	padding. If the `value` is greater than the atom length, then
 	no padding is performed.
 
+colornext::
+	Change output color only for the next atom. Followed by
+	`<:colorname>`.  Not compatible with `padright` and resets any
+	previous `color`, if set.
+
 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/ref-filter.c b/ref-filter.c
index 4c5e3f8..3ab4ab9 100644
--- a/ref-filter.c
+++ b/ref-filter.c
@@ -57,6 +57,7 @@ static struct {
 	{ "HEAD" },
 	{ "color" },
 	{ "padright" },
+	{ "colornext" },
 };
 
 /*
@@ -712,6 +713,15 @@ static void populate_value(struct ref_array_item *ref)
 			v->modifier_atom = 1;
 			v->pad_to_right = 1;
 			continue;
+		} else if (starts_with(name, "colornext:")) {
+			char color[COLOR_MAXLEN] = "";
+
+			if (color_parse(name + 10, color) < 0)
+				die(_("unable to parse format"));
+			v->s = xstrdup(color);
+			v->modifier_atom = 1;
+			v->color_next = 1;
+			continue;
 		} else
 			continue;
 
@@ -1256,7 +1266,13 @@ void ref_array_sort(struct ref_sorting *sorting, struct ref_array *array)
 static void apply_formatting_state(struct ref_formatting_state *state,
 				   struct atom_value *v, struct strbuf *value)
 {
-	if (state->pad_to_right) {
+	if (state->color_next && state->pad_to_right)
+		die(_("cannot use `colornext` and `padright` together"));
+	if (state->color_next) {
+		strbuf_addf(value, "%s%s%s", state->color_next, v->s, GIT_COLOR_RESET);
+		return;
+	}
+	else if (state->pad_to_right) {
 		if (!is_utf8(v->s))
 			strbuf_addf(value, "%-*s", state->pad_to_right, v->s);
 		else {
@@ -1346,6 +1362,8 @@ static void emit(const char *cp, const char *ep)
 static void store_formatting_state(struct ref_formatting_state *state,
 				   struct atom_value *atomv)
 {
+	if (atomv->color_next)
+		state->color_next = atomv->s;
 	if (atomv->pad_to_right)
 		state->pad_to_right = atomv->ul;
 }
diff --git a/ref-filter.h b/ref-filter.h
index fcf469e..8c82fd1 100644
--- a/ref-filter.h
+++ b/ref-filter.h
@@ -21,12 +21,14 @@ struct atom_value {
 	const char *s;
 	unsigned long ul; /* used for sorting when not FIELD_STR */
 	unsigned int modifier_atom : 1, /*  atoms which act as modifiers for the next atom */
-		pad_to_right : 1;
+		pad_to_right : 1,
+		color_next : 1;
 };
 
 struct ref_formatting_state {
 	int quote_style;
 	unsigned int pad_to_right;
+	const char *color_next;
 };
 
 struct ref_sorting {
diff --git a/t/t6302-for-each-ref-filter.sh b/t/t6302-for-each-ref-filter.sh
index 68688a9..6aad069 100755
--- a/t/t6302-for-each-ref-filter.sh
+++ b/t/t6302-for-each-ref-filter.sh
@@ -133,4 +133,20 @@ test_expect_success 'reverse version sort' '
 	test_cmp expect actual
 '
 
+get_color ()
+{
+	git config --get-color no.such.slot "$1"
+}
+
+cat >expect <<EOF &&
+$(get_color green)foo1.10$(get_color reset)||
+$(get_color green)foo1.3$(get_color reset)||
+$(get_color green)foo1.6$(get_color reset)||
+EOF
+
+test_expect_success 'check `colornext` format option' '
+	git for-each-ref --format="%(colornext:green)%(refname:short)||" | grep "foo" >actual &&
+	test_cmp expect actual
+'
+
 test_done
-- 
2.4.6