git-compat-util: convert skip_{prefix,suffix}{,_mem} to bool

Use the data type bool and its values true and false to document the
binary return value of skip_prefix() and friends more explicitly.

This first use of stdbool.h, introduced with C99, is meant to check
whether there are platforms that claim support for C99, as tested by
7bc341e21b (git-compat-util: add a test balloon for C99 support,
2021-12-01), but still lack that header for some reason.

A fallback based on a wider type, e.g. int, would have to deal with
comparisons somehow to emulate that any non-zero value is true:

   bool b1 = 1;
   bool b2 = 2;
   if (b1 == b2) puts("This is true.");

   int i1 = 1;
   int i2 = 2;
   if (i1 == i2) puts("Not printed.");
   #define BOOLEQ(a, b) (!(a) == !(b))
   if (BOOLEQ(i1, i2)) puts("This is true.");

So we'd be better off using bool everywhere without a fallback, if
possible.  That's why this patch doesn't include any.

Signed-off-by: René Scharfe <l.s.r@web.de>
Acked-by: Phillip Wood <phillip.wood@dunelm.org.uk>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

git-compat-util.h

@@ -225,6 +225,7 @@ struct strbuf;
 #include <stddef.h>
 #include <stdlib.h>
 #include <stdarg.h>
+#include <stdbool.h>
 #include <string.h>
 #ifdef HAVE_STRINGS_H
 #include <strings.h> /* for strcasecmp() */
@@ -684,11 +685,11 @@ report_fn get_warn_routine(void);
 void set_die_is_recursing_routine(int (*routine)(void));
 
 /*
- * If the string "str" begins with the string found in "prefix", return 1.
+ * If the string "str" begins with the string found in "prefix", return true.
  * The "out" parameter is set to "str + strlen(prefix)" (i.e., to the point in
  * the string right after the prefix).
  *
- * Otherwise, return 0 and leave "out" untouched.
+ * Otherwise, return false and leave "out" untouched.
  *
  * Examples:
  *
@@ -699,23 +700,23 @@ void set_die_is_recursing_routine(int (*routine)(void));
  *   [skip prefix if present, otherwise use whole string]
  *   skip_prefix(name, "refs/heads/", &name);
  */
-static inline int skip_prefix(const char *str, const char *prefix,
+static inline bool skip_prefix(const char *str, const char *prefix,
 			       const char **out)
 {
 	do {
 		if (!*prefix) {
 			*out = str;
-			return 1;
+			return true;
 		}
 	} while (*str++ == *prefix++);
-	return 0;
+	return false;
 }
 
 /*
  * Like skip_prefix, but promises never to read past "len" bytes of the input
  * buffer, and returns the remaining number of bytes in "out" via "outlen".
  */
-static inline int skip_prefix_mem(const char *buf, size_t len,
+static inline bool skip_prefix_mem(const char *buf, size_t len,
 				   const char *prefix,
 				   const char **out, size_t *outlen)
 {
@@ -723,33 +724,34 @@ static inline int skip_prefix_mem(const char *buf, size_t len,
 	if (prefix_len <= len && !memcmp(buf, prefix, prefix_len)) {
 		*out = buf + prefix_len;
 		*outlen = len - prefix_len;
-		return 1;
+		return true;
 	}
-	return 0;
+	return false;
 }
 
 /*
- * If buf ends with suffix, return 1 and subtract the length of the suffix
- * from *len. Otherwise, return 0 and leave *len untouched.
+ * If buf ends with suffix, return true and subtract the length of the suffix
+ * from *len. Otherwise, return false and leave *len untouched.
  */
-static inline int strip_suffix_mem(const char *buf, size_t *len,
+static inline bool strip_suffix_mem(const char *buf, size_t *len,
 				    const char *suffix)
 {
 	size_t suflen = strlen(suffix);
 	if (*len < suflen || memcmp(buf + (*len - suflen), suffix, suflen))
-		return 0;
+		return false;
 	*len -= suflen;
-	return 1;
+	return true;
 }
 
 /*
- * If str ends with suffix, return 1 and set *len to the size of the string
- * without the suffix. Otherwise, return 0 and set *len to the size of the
+ * If str ends with suffix, return true and set *len to the size of the string
+ * without the suffix. Otherwise, return false and set *len to the size of the
  * string.
  *
  * Note that we do _not_ NUL-terminate str to the new length.
  */
-static inline int strip_suffix(const char *str, const char *suffix, size_t *len)
+static inline bool strip_suffix(const char *str, const char *suffix,
+				size_t *len)
 {
 	*len = strlen(str);
 	return strip_suffix_mem(str, len, suffix);