[PATCH v2 4/6] cocci: add "string_list" rule to swap "DUP" <-> "NODUP"

["Ævar Arnfjörð Bjarmason" <avarab@gmail.com>]

Add a coccinelle rule to swap "NODUP" and "DUP" initialization in
cases such as [1], which as this change shows produces an identical
change.

We happened to have only one change in-tree that matched this
criteria, but now we're more certain of that, and will convert these
sorts of cases in the future.

1. https://lore.kernel.org/git/xmqq7d471dns.fsf@gitster.g/

Signed-off-by: Ævar Arnfjörð Bjarmason <avarab@gmail.com>
---
 builtin/remote.c                         |  3 +--
 contrib/coccinelle/string-list.cocci     | 18 ++++++++++++++++++
 contrib/coccinelle/tests/string-list.c   | 13 +++++++++++++
 contrib/coccinelle/tests/string-list.res | 11 +++++++++++
 4 files changed, 43 insertions(+), 2 deletions(-)

diff --git a/builtin/remote.c b/builtin/remote.c
index d9b8746cb3c..c713463d89d 100644
--- a/builtin/remote.c
+++ b/builtin/remote.c
@@ -1229,10 +1229,9 @@ static int get_one_entry(struct remote *remote, void *priv)
 
 static int show_all(void)
 {
-	struct string_list list = STRING_LIST_INIT_NODUP;
+	struct string_list list = STRING_LIST_INIT_DUP;
 	int result;
 
-	list.strdup_strings = 1;
 	result = for_each_remote(get_one_entry, &list);
 
 	if (!result) {
diff --git a/contrib/coccinelle/string-list.cocci b/contrib/coccinelle/string-list.cocci
index 5d285d5732c..63bb2abc93a 100644
--- a/contrib/coccinelle/string-list.cocci
+++ b/contrib/coccinelle/string-list.cocci
@@ -6,3 +6,21 @@ struct string_list *P;
 ... when != P
 - (P)->strdup_strings = 1;
 + string_list_init_dup(P);
+
+@@
+type T;
+identifier I;
+constant INIT_NODUP =~ "^STRING_LIST_INIT_NODUP$";
+constant INIT_DUP =~ "^STRING_LIST_INIT_DUP$";
+@@
+(
+- T I = INIT_NODUP;
++ T I = STRING_LIST_INIT_DUP;
+... when != &I
+- I.strdup_strings = 1;
+|
+- T I = INIT_DUP;
++ T I = STRING_LIST_INIT_NODUP;
+... when != &I
+- I.strdup_strings = 0;
+)
diff --git a/contrib/coccinelle/tests/string-list.c b/contrib/coccinelle/tests/string-list.c
index e77822b7682..1821ed4ebb4 100644
--- a/contrib/coccinelle/tests/string-list.c
+++ b/contrib/coccinelle/tests/string-list.c
@@ -1,7 +1,20 @@
 int init(void)
 {
 	struct string_list *list;
+	struct string_list list2 = STRING_LIST_INIT_NODUP;
+	struct string_list list3 = STRING_LIST_INIT_DUP;
+	struct string_list list4 = STRING_LIST_INIT_NODUP;
+	struct string_list list5 = STRING_LIST_INIT_DUP;
 
 	CALLOC_ARRAY(list, 1);
+
+	/* Exclude these */
+	string_list_append(&list4, "str");
+	string_list_append_nodup(&list5, xstrdup("str"));
+
 	list->strdup_strings = 1;
+	list2.strdup_strings = 1;
+	list3.strdup_strings = 0;
+	list4.strdup_strings = 1;
+	list5.strdup_strings = 0;
 }
diff --git a/contrib/coccinelle/tests/string-list.res b/contrib/coccinelle/tests/string-list.res
index 7e666f5bf48..58b3733dec2 100644
--- a/contrib/coccinelle/tests/string-list.res
+++ b/contrib/coccinelle/tests/string-list.res
@@ -1,7 +1,18 @@
 int init(void)
 {
 	struct string_list *list;
+	struct string_list list2 = STRING_LIST_INIT_DUP;
+	struct string_list list3 = STRING_LIST_INIT_NODUP;
+	struct string_list list4 = STRING_LIST_INIT_NODUP;
+	struct string_list list5 = STRING_LIST_INIT_DUP;
 
 	ALLOC_ARRAY(list, 1);
+
+	/* Exclude these */
+	string_list_append(&list4, "str");
+	string_list_append_nodup(&list5, xstrdup("str"));
+
 	string_list_init_dup(list);
+	list4.strdup_strings = 1;
+	list5.strdup_strings = 0;
 }
-- 
2.37.1.1095.g64a1e8362fd