Fix bogus error message from merge-recursive error path

This error message should not usually trigger, but the function
make_cache_entry() called by add_cacheinfo() can return early
without calling into refresh_cache_entry() that sets cache_errno.

Also the error message had a wrong function name reported, and
it did not say anything about which path failed either.
Signed-off-by: NJunio C Hamano <junkio@cox.net>

cache.h

@@ -128,7 +128,6 @@ static inline unsigned int ce_mode_from_stat(struct cache_entry *ce, unsigned in
 extern struct cache_entry **active_cache;
 extern unsigned int active_nr, active_alloc, active_cache_changed;
 extern struct cache_tree *active_cache_tree;
-extern int cache_errno;
 
 enum object_type {
 	OBJ_BAD = -1,

merge-recursive.c

@@ -221,7 +221,7 @@ static int add_cacheinfo(unsigned int mode, const unsigned char *sha1,
 	struct cache_entry *ce;
 	ce = make_cache_entry(mode, sha1 ? sha1 : null_sha1, path, stage, refresh);
 	if (!ce)
-		return error("cache_addinfo failed: %s", strerror(cache_errno));
+		return error("addinfo_cache failed for path '%s'", path);
 	return add_cache_entry(ce, options);
 }
 

read-cache.c

@@ -24,7 +24,7 @@ unsigned int active_nr, active_alloc, active_cache_changed;
 
 struct cache_tree *active_cache_tree;
 
-int cache_errno;
+static int cache_errno;
 
 static void *cache_mmap;
 static size_t cache_mmap_size;