Merge branch 'pw/adopt-c99-bool-officially'

Declare weather-balloon we raised for "bool" type 18 months ago a
success and officially allow using the type in our codebase.

* pw/adopt-c99-bool-officially:
  strbuf: convert predicates to return bool
  git-compat-util: convert string predicates to return bool
  CodingGuidelines: allow the use of bool

Documentation/CodingGuidelines

@@ -298,6 +298,9 @@ For C programs:
    . since late 2021 with 44ba10d6, we have had variables declared in
      the for loop "for (int i = 0; i < 10; i++)".
 
+   . since late 2023 with 8277dbe987 we have been using the bool type
+     from <stdbool.h>.
+
    New C99 features that we cannot use yet:
 
    . %z and %zu as a printf() argument for a size_t (the %z being for

git-compat-util.h

@@ -897,16 +897,16 @@ static inline size_t xsize_t(off_t len)
  * is done via tolower(), so it is strictly ASCII (no multi-byte characters or
  * locale-specific conversions).
  */
-static inline int skip_iprefix(const char *str, const char *prefix,
+static inline bool skip_iprefix(const char *str, const char *prefix,
 			       const char **out)
 {
 	do {
 		if (!*prefix) {
 			*out = str;
-			return 1;
+			return true;
 		}
 	} while (tolower(*str++) == tolower(*prefix++));
-	return 0;
+	return false;
 }
 
 /*
@@ -914,7 +914,7 @@ static inline int skip_iprefix(const char *str, const char *prefix,
  * comparison is done via tolower(), so it is strictly ASCII (no multi-byte
  * characters or locale-specific conversions).
  */
-static inline int skip_iprefix_mem(const char *buf, size_t len,
+static inline bool skip_iprefix_mem(const char *buf, size_t len,
 				   const char *prefix,
 				   const char **out, size_t *outlen)
 {
@@ -922,10 +922,10 @@ static inline int skip_iprefix_mem(const char *buf, size_t len,
 		if (!*prefix) {
 			*out = buf;
 			*outlen = len;
-			return 1;
+			return true;
 		}
 	} while (len-- > 0 && tolower(*buf++) == tolower(*prefix++));
-	return 0;
+	return false;
 }
 
 static inline int strtoul_ui(char const *s, int base, unsigned int *result)

strbuf.c

@@ -8,55 +8,55 @@
 #include "utf8.h"
 #include "date.h"
 
-int starts_with(const char *str, const char *prefix)
+bool starts_with(const char *str, const char *prefix)
 {
 	for (; ; str++, prefix++)
 		if (!*prefix)
-			return 1;
+			return true;
 		else if (*str != *prefix)
-			return 0;
+			return false;
 }
 
-int istarts_with(const char *str, const char *prefix)
+bool istarts_with(const char *str, const char *prefix)
 {
 	for (; ; str++, prefix++)
 		if (!*prefix)
-			return 1;
+			return true;
 		else if (tolower(*str) != tolower(*prefix))
-			return 0;
+			return false;
 }
 
-int starts_with_mem(const char *str, size_t len, const char *prefix)
+bool starts_with_mem(const char *str, size_t len, const char *prefix)
 {
 	const char *end = str + len;
 	for (; ; str++, prefix++) {
 		if (!*prefix)
-			return 1;
+			return true;
 		else if (str == end || *str != *prefix)
-			return 0;
+			return false;
 	}
 }
 
-int skip_to_optional_arg_default(const char *str, const char *prefix,
+bool skip_to_optional_arg_default(const char *str, const char *prefix,
 				 const char **arg, const char *def)
 {
 	const char *p;
 
 	if (!skip_prefix(str, prefix, &p))
-		return 0;
+		return false;
 
 	if (!*p) {
 		if (arg)
 			*arg = def;
-		return 1;
+		return true;
 	}
 
 	if (*p != '=')
-		return 0;
+		return false;
 
 	if (arg)
 		*arg = p + 1;
-	return 1;
+	return true;
 }
 
 /*

strbuf.h

@@ -660,9 +660,9 @@ char *xstrvfmt(const char *fmt, va_list ap);
 __attribute__((format (printf, 1, 2)))
 char *xstrfmt(const char *fmt, ...);
 
-int starts_with(const char *str, const char *prefix);
+bool starts_with(const char *str, const char *prefix);
-int istarts_with(const char *str, const char *prefix);
+bool istarts_with(const char *str, const char *prefix);
-int starts_with_mem(const char *str, size_t len, const char *prefix);
+bool starts_with_mem(const char *str, size_t len, const char *prefix);
 
 /*
  * If the string "str" is the same as the string in "prefix", then the "arg"
@@ -678,16 +678,16 @@ int starts_with_mem(const char *str, size_t len, const char *prefix);
  * can be used instead of !strcmp(arg, "--key") and then
  * skip_prefix(arg, "--key=", &arg) to parse such an option.
  */
-int skip_to_optional_arg_default(const char *str, const char *prefix,
+bool skip_to_optional_arg_default(const char *str, const char *prefix,
 				 const char **arg, const char *def);
 
-static inline int skip_to_optional_arg(const char *str, const char *prefix,
+static inline bool skip_to_optional_arg(const char *str, const char *prefix,
 				       const char **arg)
 {
 	return skip_to_optional_arg_default(str, prefix, arg, "");
 }
 
-static inline int ends_with(const char *str, const char *suffix)
+static inline bool ends_with(const char *str, const char *suffix)
 {
 	size_t len;
 	return strip_suffix(str, suffix, &len);