diff --git a/add-interactive.c b/add-interactive.c
index 6ffe64c38d..68fc09547d 100644
--- a/add-interactive.c
+++ b/add-interactive.c
@@ -244,7 +244,8 @@ static void find_unique_prefixes(struct prefix_item_list *list)
 
 static ssize_t find_unique(const char *string, struct prefix_item_list *list)
 {
-	int index = string_list_find_insert_index(&list->sorted, string, 1);
+	bool 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)
@@ -252,8 +253,8 @@ static ssize_t find_unique(const char *string, struct prefix_item_list *list)
 		    " vs %"PRIuMAX")",
 		    (uintmax_t)list->items.nr, (uintmax_t)list->sorted.nr);
 
-	if (index < 0)
-		item = list->sorted.items[-1 - index].util;
+	if (exact_match)
+		item = list->sorted.items[index].util;
 	else if (index > 0 &&
 		 starts_with(list->sorted.items[index - 1].string, string))
 		return -1;
diff --git a/mailmap.c b/mailmap.c
index 56c72102d9..37fd158a51 100644
--- a/mailmap.c
+++ b/mailmap.c
@@ -1,5 +1,4 @@
 #define USE_THE_REPOSITORY_VARIABLE
-#define DISABLE_SIGN_COMPARE_WARNINGS
 
 #include "git-compat-util.h"
 #include "environment.h"
@@ -243,10 +242,9 @@ void clear_mailmap(struct string_list *map)
 static struct string_list_item *lookup_prefix(struct string_list *map,
 					      const char *string, size_t len)
 {
-	int i = string_list_find_insert_index(map, string, 1);
-	if (i < 0) {
-		/* exact match */
-		i = -1 - i;
+	bool exact_match;
+	size_t i = string_list_find_insert_index(map, string, &exact_match);
+	if (exact_match) {
 		if (!string[len])
 			return &map->items[i];
 		/*
@@ -267,7 +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)
 			/*
diff --git a/refs.c b/refs.c
index c83e3d7a4d..965381367e 100644
--- a/refs.c
+++ b/refs.c
@@ -3,7 +3,6 @@
  */
 
 #define USE_THE_REPOSITORY_VARIABLE
-#define DISABLE_SIGN_COMPARE_WARNINGS
 
 #include "git-compat-util.h"
 #include "advice.h"
@@ -1714,8 +1713,6 @@ const char *find_descendant_ref(const char *dirname,
 				const struct string_list *extras,
 				const struct string_list *skip)
 {
-	int pos;
-
 	if (!extras)
 		return NULL;
 
@@ -1725,7 +1722,7 @@ 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, 0);
+	for (size_t pos = string_list_find_insert_index(extras, dirname, NULL);
 	     pos < extras->nr; pos++) {
 		const char *extra_refname = extras->items[pos].string;
 
@@ -2414,7 +2411,7 @@ static int run_transaction_hook(struct ref_transaction *transaction,
 	struct child_process proc = CHILD_PROCESS_INIT;
 	struct strbuf buf = STRBUF_INIT;
 	const char *hook;
-	int ret = 0, i;
+	int ret = 0;
 
 	hook = find_hook(transaction->ref_store->repo, "reference-transaction");
 	if (!hook)
@@ -2431,7 +2428,7 @@ static int run_transaction_hook(struct ref_transaction *transaction,
 
 	sigchain_push(SIGPIPE, SIG_IGN);
 
-	for (i = 0; i < transaction->nr; i++) {
+	for (size_t i = 0; i < transaction->nr; i++) {
 		struct ref_update *update = transaction->updates[i];
 
 		if (update->flags & REF_LOG_ONLY)
@@ -2824,9 +2821,7 @@ void ref_transaction_for_each_queued_update(struct ref_transaction *transaction,
 					    ref_transaction_for_each_queued_update_fn cb,
 					    void *cb_data)
 {
-	int i;
-
-	for (i = 0; i < transaction->nr; i++) {
+	for (size_t i = 0; i < transaction->nr; i++) {
 		struct ref_update *update = transaction->updates[i];
 
 		cb(update->refname,
diff --git a/string-list.c b/string-list.c
index 343cf1ca90..08dc00984c 100644
--- a/string-list.c
+++ b/string-list.c
@@ -16,7 +16,7 @@ void string_list_init_dup(struct string_list *list)
 /* if there is no exact match, point to the index where the entry could be
  * inserted */
 static size_t get_entry_index(const struct string_list *list, const char *string,
-			      int *exact_match)
+			      bool *exact_match)
 {
 	size_t left = 0, right = list->nr;
 	compare_strings_fn cmp = list->cmp ? list->cmp : strcmp;
@@ -29,18 +29,20 @@ static size_t get_entry_index(const struct string_list *list, const char *string
 		else if (compare > 0)
 			left = middle + 1;
 		else {
-			*exact_match = 1;
+			if (exact_match)
+				*exact_match = true;
 			return middle;
 		}
 	}
 
-	*exact_match = 0;
+	if (exact_match)
+		*exact_match = false;
 	return right;
 }
 
 static size_t add_entry(struct string_list *list, const char *string)
 {
-	int exact_match = 0;
+	bool exact_match;
 	size_t index = get_entry_index(list, string, &exact_match);
 
 	if (exact_match)
@@ -68,7 +70,7 @@ struct string_list_item *string_list_insert(struct string_list *list, const char
 void string_list_remove(struct string_list *list, const char *string,
 			int free_util)
 {
-	int exact_match;
+	bool exact_match;
 	int i = get_entry_index(list, string, &exact_match);
 
 	if (exact_match) {
@@ -82,26 +84,23 @@ void string_list_remove(struct string_list *list, const char *string,
 	}
 }
 
-int string_list_has_string(const struct string_list *list, const char *string)
+bool string_list_has_string(const struct string_list *list, const char *string)
 {
-	int exact_match;
+	bool exact_match;
 	get_entry_index(list, string, &exact_match);
 	return exact_match;
 }
 
-int string_list_find_insert_index(const struct string_list *list, const char *string,
-				  int negative_existing_index)
+size_t string_list_find_insert_index(const struct string_list *list, const char *string,
+				     bool *exact_match)
 {
-	int exact_match;
-	int index = get_entry_index(list, string, &exact_match);
-	if (exact_match)
-		index = -1 - (negative_existing_index ? index : 0);
-	return index;
+	return get_entry_index(list, string, exact_match);
 }
 
 struct string_list_item *string_list_lookup(struct string_list *list, const char *string)
 {
-	int exact_match, i = get_entry_index(list, string, &exact_match);
+	bool exact_match;
+	size_t i = get_entry_index(list, string, &exact_match);
 	if (!exact_match)
 		return NULL;
 	return list->items + i;
diff --git a/string-list.h b/string-list.h
index 2b438c7733..fa6ba07853 100644
--- a/string-list.h
+++ b/string-list.h
@@ -172,9 +172,15 @@ void string_list_remove_empty_items(struct string_list *list, int free_util);
 /* Use these functions only on sorted lists: */
 
 /** Determine if the string_list has a given string or not. */
-int 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,
-				  int negative_existing_index);
+bool string_list_has_string(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);
 
 /**
  * Insert a new element to the string_list. The returned pointer can