use xstrncmpz()

Add and apply a semantic patch for calling xstrncmpz() to compare a
NUL-terminated string with a buffer of a known length instead of using
strncmp() and checking the terminating NUL explicitly.  This simplifies
callers by reducing code duplication.

I had to adjust remote.c manually because Coccinelle inexplicably
changed the indent of the else branches.

Signed-off-by: René Scharfe <l.s.r@web.de>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

archive-tar.c

@@ -365,7 +365,7 @@ static struct archiver *find_tar_filter(const char *name, size_t len)
 	int i;
 	for (i = 0; i < nr_tar_filters; i++) {
 		struct archiver *ar = tar_filters[i];
-		if (!strncmp(ar->name, name, len) && !ar->name[len])
+		if (!xstrncmpz(ar->name, name, len))
 			return ar;
 	}
 	return NULL;

builtin/fast-export.c

@@ -136,8 +136,7 @@ static int anonymized_entry_cmp(const void *cmp_data UNUSED,
 	a = container_of(eptr, const struct anonymized_entry, hash);
 	if (keydata) {
 		const struct anonymized_entry_key *key = keydata;
-		int equal = !strncmp(a->orig, key->orig, key->orig_len) &&
+		int equal = !xstrncmpz(a->orig, key->orig, key->orig_len);
-			    !a->orig[key->orig_len];
 		return !equal;
 	}
 

builtin/merge.c

@@ -192,8 +192,7 @@ static struct strategy *get_strategy(const char *name)
 			int j, found = 0;
 			struct cmdname *ent = main_cmds.names[i];
 			for (j = 0; !found && j < ARRAY_SIZE(all_strategy); j++)
-				if (!strncmp(ent->name, all_strategy[j].name, ent->len)
+				if (!xstrncmpz(all_strategy[j].name, ent->name, ent->len))
-						&& !all_strategy[j].name[ent->len])
 					found = 1;
 			if (!found)
 				add_cmdname(&not_strategies, ent->name, ent->len);

builtin/reflog.c

@@ -96,8 +96,7 @@ static struct reflog_expire_cfg *find_cfg_ent(const char *pattern, size_t len)
 		reflog_expire_cfg_tail = &reflog_expire_cfg;
 
 	for (ent = reflog_expire_cfg; ent; ent = ent->next)
-		if (!strncmp(ent->pattern, pattern, len) &&
+		if (!xstrncmpz(ent->pattern, pattern, len))
-		    ent->pattern[len] == '\0')
 			return ent;
 
 	FLEX_ALLOC_MEM(ent, pattern, pattern, len);

contrib/coccinelle/xstrncmpz.cocci

@@ -0,0 +1,28 @@
+@@
+expression S, T, L;
+@@
+(
+- strncmp(S, T, L) || S[L]
++ !!xstrncmpz(S, T, L)
+|
+- strncmp(S, T, L) || S[L] != '\0'
++ !!xstrncmpz(S, T, L)
+|
+- strncmp(S, T, L) || T[L]
++ !!xstrncmpz(T, S, L)
+|
+- strncmp(S, T, L) || T[L] != '\0'
++ !!xstrncmpz(T, S, L)
+|
+- !strncmp(S, T, L) && !S[L]
++ !xstrncmpz(S, T, L)
+|
+- !strncmp(S, T, L) && S[L] == '\0'
++ !xstrncmpz(S, T, L)
+|
+- !strncmp(S, T, L) && !T[L]
++ !xstrncmpz(T, S, L)
+|
+- !strncmp(S, T, L) && T[L] == '\0'
++ !xstrncmpz(T, S, L)
+)

convert.c

@@ -1028,7 +1028,7 @@ static int read_convert_config(const char *var, const char *value,
 	if (parse_config_key(var, "filter", &name, &namelen, &key) < 0 || !name)
 		return 0;
 	for (drv = user_convert; drv; drv = drv->next)
-		if (!strncmp(drv->name, name, namelen) && !drv->name[namelen])
+		if (!xstrncmpz(drv->name, name, namelen))
 			break;
 	if (!drv) {
 		CALLOC_ARRAY(drv, 1);

merge-ll.c

@@ -286,7 +286,7 @@ static int read_merge_config(const char *var, const char *value,
 	 * after seeing merge.<name>.var1.
 	 */
 	for (fn = ll_user_merge; fn; fn = fn->next)
-		if (!strncmp(fn->name, name, namelen) && !fn->name[namelen])
+		if (!xstrncmpz(fn->name, name, namelen))
 			break;
 	if (!fn) {
 		CALLOC_ARRAY(fn, 1);

object.c

@@ -47,8 +47,7 @@ int type_from_string_gently(const char *str, ssize_t len, int gentle)
 		len = strlen(str);
 
 	for (i = 1; i < ARRAY_SIZE(object_type_strings); i++)
-		if (!strncmp(str, object_type_strings[i], len) &&
+		if (!xstrncmpz(object_type_strings[i], str, len))
-		    object_type_strings[i][len] == '\0')
 			return i;
 
 	if (gentle)

remote.c

@@ -105,7 +105,7 @@ static int remotes_hash_cmp(const void *cmp_data UNUSED,
 	b = container_of(entry_or_key, const struct remote, ent);
 
 	if (key)
-		return strncmp(a->name, key->str, key->len) || a->name[key->len];
+		return !!xstrncmpz(a->name, key->str, key->len);
 	else
 		return strcmp(a->name, b->name);
 }
@@ -189,8 +189,7 @@ static int branches_hash_cmp(const void *cmp_data UNUSED,
 	b = container_of(entry_or_key, const struct branch, ent);
 
 	if (key)
-		return strncmp(a->name, key->str, key->len) ||
+		return !!xstrncmpz(a->name, key->str, key->len);
-		       a->name[key->len];
 	else
 		return strcmp(a->name, b->name);
 }

userdiff.c

@@ -323,8 +323,7 @@ static int userdiff_find_by_namelen_cb(struct userdiff_driver *driver,
 {
 	struct find_by_namelen_data *cb_data = priv;
 
-	if (!strncmp(driver->name, cb_data->name, cb_data->len) &&
+	if (!xstrncmpz(driver->name, cb_data->name, cb_data->len)) {
-	    !driver->name[cb_data->len]) {
 		cb_data->driver = driver;
 		return 1; /* tell the caller to stop iterating */
 	}