update-index --refresh --porcelain: add missing const

Signed-off-by: Jonathan Nieder <jrnieder@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

cache.h

@@ -511,7 +511,7 @@ extern void fill_stat_cache_info(struct cache_entry *ce, struct stat *st);
 #define REFRESH_IGNORE_MISSING	0x0008	/* ignore non-existent */
 #define REFRESH_IGNORE_SUBMODULES	0x0010	/* ignore submodules */
 #define REFRESH_IN_PORCELAIN	0x0020	/* user friendly output, not "needs update" */
-extern int refresh_index(struct index_state *, unsigned int flags, const char **pathspec, char *seen, char *header_msg);
+extern int refresh_index(struct index_state *, unsigned int flags, const char **pathspec, char *seen, const char *header_msg);
 
 struct lock_file {
 	struct lock_file *next;

read-cache.c

@@ -1104,7 +1104,7 @@ static struct cache_entry *refresh_cache_ent(struct index_state *istate,
 }
 
 static void show_file(const char * fmt, const char * name, int in_porcelain,
-		      int * first, char *header_msg)
+		      int * first, const char *header_msg)
 {
 	if (in_porcelain && *first && header_msg) {
 		printf("%s\n", header_msg);
@@ -1114,7 +1114,7 @@ static void show_file(const char * fmt, const char * name, int in_porcelain,
 }
 
 int refresh_index(struct index_state *istate, unsigned int flags, const char **pathspec,
-		  char *seen, char *header_msg)
+		  char *seen, const char *header_msg)
 {
 	int i;
 	int has_errors = 0;