pathspec: match and original in pathspec_item are const

[Junio C Hamano <gitster@pobox.com>]

Junio C Hamano <gitster@pobox.com> writes:

> This unfortunately triggers
>
> t/unit-tests/u-dir.c: In function 'test_dir__common_prefix_skips_excluded_pathspec_items':
> t/unit-tests/u-dir.c:53:34: error: initialization discards 'const' qualifier from pointer target type [-Werror=discarded-qualifiers]
>    53 |                         .match = "unrelated/path",
>       |                                  ^~~~~~~~~~~~~~~~
>
> Other than that, looking good.

We may want a preparatory patch before this step.

----- >8 -----
Subject: pathspec: match and original in pathspec_item are const

No existing code modifies these two strings in pathspec elements
after they are created via these two pointers.  Declare them as
"const char *" to stress on this fact and cast away constness from
the code that frees these two strings.

Signed-off-by: Junio C Hamano <gitster@pobox.com>
---
 pathspec.c | 4 ++--
 pathspec.h | 4 ++--
 2 files changed, 4 insertions(+), 4 deletions(-)

diff --git c/pathspec.c w/pathspec.c
index f78b22709c..06b7065372 100644
--- c/pathspec.c
+++ w/pathspec.c
@@ -749,8 +749,8 @@ void clear_pathspec(struct pathspec *pathspec)
 	int i, j;
 
 	for (i = 0; i < pathspec->nr; i++) {
-		free(pathspec->items[i].match);
-		free(pathspec->items[i].original);
+		free((void *)pathspec->items[i].match);
+		free((void *)pathspec->items[i].original);
 
 		for (j = 0; j < pathspec->items[i].attr_match_nr; j++)
 			free(pathspec->items[i].attr_match[j].value);
diff --git c/pathspec.h w/pathspec.h
index 5e3a6f1fe7..fc1b9465ad 100644
--- c/pathspec.h
+++ w/pathspec.h
@@ -35,8 +35,8 @@ struct pathspec {
 	unsigned magic;
 	int max_depth;
 	struct pathspec_item {
-		char *match;
-		char *original;
+		const char *match;
+		const char *original;
 		unsigned magic;
 		int len, prefix;
 		int nowildcard_len;