[PATCH v2 02/10] ref-filter: implement %(if:equals=<string>) and %(if:notequals=<string>)

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

Implement %(if:equals=<string>) wherein the if condition is only
satisfied if the value obtained between the %(if:...) and %(then) atom
is the same as the given '<string>'.

Similarly, implement (if:notequals=<string>) wherein the if condition
is only satisfied if the value obtained between the %(if:...) and
%(then) atom is differnt from the given '<string>'.

Add tests and Documentation for the same.

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 |  4 +++-
 ref-filter.c                       | 28 ++++++++++++++++++++++++----
 t/t6302-for-each-ref-filter.sh     | 18 ++++++++++++++++++
 3 files changed, 45 insertions(+), 5 deletions(-)

diff --git a/Documentation/git-for-each-ref.txt b/Documentation/git-for-each-ref.txt
index 7345acb..206d646 100644
--- a/Documentation/git-for-each-ref.txt
+++ b/Documentation/git-for-each-ref.txt
@@ -144,7 +144,9 @@ if::
 	printed. We ignore space when evaluating the string before
 	%(then), this is useful when we use the %(HEAD) atom which
 	prints either "*" or " " and we want to apply the 'if'
-	condition only on the 'HEAD' ref.
+	condition only on the 'HEAD' ref. Append ":equals=<string>" or
+	":notequals=<string>" to compare the value between the
+	%(if:...) and %(then) atoms with the given string.
 
 In addition to the above, for commit and tag objects, the header
 field names (`tree`, `parent`, `object`, `type`, and `tag`) can
diff --git a/ref-filter.c b/ref-filter.c
index 95f007c..359c76d 100644
--- a/ref-filter.c
+++ b/ref-filter.c
@@ -73,6 +73,8 @@ struct contents {
 };
 
 struct if_then_else {
+	const char *if_equals,
+		*not_equals;
 	unsigned int then_atom : 1,
 		else_atom : 1,
 		condition_satisfied : 1;
@@ -281,6 +283,14 @@ static void if_atom_handler(struct atom_value *atomv, struct ref_formatting_stat
 {
 	struct ref_formatting_stack *new;
 	struct if_then_else *if_then_else = xcalloc(sizeof(struct if_then_else), 1);
+	const char *valp;
+
+	if (skip_prefix(atomv->s, "equals=", &valp))
+		if_then_else->if_equals = valp;
+	else if (skip_prefix(atomv->s, "notequals=", &valp))
+		if_then_else->not_equals = valp;
+	else if (atomv->s[0])
+		die(_("format: unknown format if:%s"), atomv->s);
 
 	push_stack_element(&state->stack);
 	new = state->stack;
@@ -309,11 +319,19 @@ static void then_atom_handler(struct atom_value *atomv, struct ref_formatting_st
 	if (if_then_else->then_atom)
 		die(_("format: %%(then) atom used more than once"));
 	if_then_else->then_atom = 1;
+
 	/*
-	 * If there exists non-empty string between the 'if' and
-	 * 'then' atom then the 'if' condition is satisfied.
+	 * If the 'equals' or 'notequals' attribute is used then
+	 * perform the required comparison. If not, only non-empty
+	 * strings satisfy the 'if' condition.
 	 */
-	if (cur->output.len && !is_empty(cur->output.buf))
+	if (if_then_else->if_equals) {
+		if (!strcmp(if_then_else->if_equals, cur->output.buf))
+			if_then_else->condition_satisfied = 1;
+	} else 	if (if_then_else->not_equals) {
+		if (strcmp(if_then_else->not_equals, cur->output.buf))
+			if_then_else->condition_satisfied = 1;
+	} else if (cur->output.len && !is_empty(cur->output.buf))
 		if_then_else->condition_satisfied = 1;
 	strbuf_reset(&cur->output);
 }
@@ -1024,8 +1042,10 @@ static void populate_value(struct ref_array_item *ref)
 		} else if (!strcmp(name, "end")) {
 			v->handler = end_atom_handler;
 			continue;
-		} else if (!strcmp(name, "if")) {
+		} else if (match_atom_name(name, "if", &valp)) {
 			v->handler = if_atom_handler;
+			if (valp)
+				v->s = xstrdup(valp);
 			continue;
 		} else if (!strcmp(name, "then")) {
 			v->handler = then_atom_handler;
diff --git a/t/t6302-for-each-ref-filter.sh b/t/t6302-for-each-ref-filter.sh
index 617fa1f..f45ac1f 100755
--- a/t/t6302-for-each-ref-filter.sh
+++ b/t/t6302-for-each-ref-filter.sh
@@ -322,4 +322,22 @@ test_expect_success 'ignore spaces in %(if) atom usage' '
 	test_cmp expect actual
 '
 
+test_expect_success 'check %(if:equals=<string>)' '
+	git for-each-ref --format="%(if:equals=master)%(refname:short)%(then)Found master%(else)Not master%(end)" refs/heads/ >actual &&
+	cat >expect <<-\EOF &&
+	Found master
+	Not master
+	EOF
+	test_cmp expect actual
+'
+
+test_expect_success 'check %(if:notequals=<string>)' '
+	git for-each-ref --format="%(if:notequals=master)%(refname:short)%(then)Not master%(else)Found master%(end)" refs/heads/ >actual &&
+	cat >expect <<-\EOF &&
+	Found master
+	Not master
+	EOF
+	test_cmp expect actual
+'
+
 test_done
-- 
2.6.0