string-list: change "string_list_find_insert_index" return type to "size_t"

As "string_list_find_insert_index" is a simple wrapper of
"get_entry_index" and the return type of "get_entry_index" is already
"size_t", we could simply change its return type to "size_t".

Update all callers to use size_t variables for storing the return value.
The tricky fix is the loop condition in "mailmap.c" to properly handle
"size_t" underflow by changing from `0 <= --i` to `i--`.

Remove "DISABLE_SIGN_COMPARE_WARNINGS" from "mailmap.c" as it's no
longer needed with the proper unsigned types.

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

add-interactive.c

@@ -222,7 +222,7 @@ static void find_unique_prefixes(struct prefix_item_list *list)
 static ssize_t find_unique(const char *string, struct prefix_item_list *list)
 {
 	bool exact_match;
-	int index = string_list_find_insert_index(&list->sorted, string, &exact_match);
+	size_t index = string_list_find_insert_index(&list->sorted, string, &exact_match);
 	struct string_list_item *item;
 
 	if (list->items.nr != list->sorted.nr)

mailmap.c

@@ -1,5 +1,4 @@
 #define USE_THE_REPOSITORY_VARIABLE
-#define DISABLE_SIGN_COMPARE_WARNINGS
 
 #include "git-compat-util.h"
 #include "environment.h"
@@ -244,7 +243,7 @@ static struct string_list_item *lookup_prefix(struct string_list *map,
 					      const char *string, size_t len)
 {
 	bool exact_match;
-	int i = string_list_find_insert_index(map, string, &exact_match);
+	size_t i = string_list_find_insert_index(map, string, &exact_match);
 	if (exact_match) {
 		if (!string[len])
 			return &map->items[i];
@@ -266,7 +265,7 @@ static struct string_list_item *lookup_prefix(struct string_list *map,
 	 * overlong key would be inserted, which must come after the
 	 * real location of the key if one exists.
 	 */
-	while (0 <= --i && i < map->nr) {
+	while (i-- && i < map->nr) {
 		int cmp = strncasecmp(map->items[i].string, string, len);
 		if (cmp < 0)
 			/*

refs.c

@@ -1688,8 +1688,6 @@ const char *find_descendant_ref(const char *dirname,
 				const struct string_list *extras,
 				const struct string_list *skip)
 {
-	int pos;
-
 	if (!extras)
 		return NULL;
 
@@ -1699,7 +1697,7 @@ const char *find_descendant_ref(const char *dirname,
 	 * with dirname (remember, dirname includes the trailing
 	 * slash) and is not in skip, then we have a conflict.
 	 */
-	for (pos = string_list_find_insert_index(extras, dirname, NULL);
+	for (size_t pos = string_list_find_insert_index(extras, dirname, NULL);
 	     pos < extras->nr; pos++) {
 		const char *extra_refname = extras->items[pos].string;
 

string-list.c

@@ -91,7 +91,7 @@ bool string_list_has_string(const struct string_list *list, const char *string)
 	return exact_match;
 }
 
-int string_list_find_insert_index(const struct string_list *list, const char *string,
+size_t string_list_find_insert_index(const struct string_list *list, const char *string,
 				     bool *exact_match)
 {
 	return get_entry_index(list, string, exact_match);

string-list.h

@@ -173,7 +173,13 @@ void string_list_remove_empty_items(struct string_list *list, int free_util);
 
 /** Determine if the string_list has a given string or not. */
 bool string_list_has_string(const struct string_list *list, const char *string);
-int string_list_find_insert_index(const struct string_list *list, const char *string,
+
+/**
+ * Find the index at which a new element should be inserted into the
+ * string_list to maintain sorted order. If exact_match is not NULL,
+ * it will be set to true if the string already exists in the list.
+ */
+size_t string_list_find_insert_index(const struct string_list *list, const char *string,
 				     bool *exact_match);
 
 /**