ctype: implement islower/isupper macro

"perf" uses a the forked copy of this file, and wants to use these two
macros.

Signed-off-by: Namhyung Kim <namhyung.kim@lge.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

Author: Namhyung Kim

git-compat-util.h

@@ -463,6 +463,8 @@ static inline int has_extension(const char *filename, const char *ext)
 #undef isdigit
 #undef isalpha
 #undef isalnum
+#undef islower
+#undef isupper
 #undef tolower
 #undef toupper
 extern unsigned char sane_ctype[256];
@@ -478,6 +480,8 @@ extern unsigned char sane_ctype[256];
 #define isdigit(x) sane_istest(x,GIT_DIGIT)
 #define isalpha(x) sane_istest(x,GIT_ALPHA)
 #define isalnum(x) sane_istest(x,GIT_ALPHA | GIT_DIGIT)
+#define islower(x) sane_iscase(x, 1)
+#define isupper(x) sane_iscase(x, 0)
 #define is_glob_special(x) sane_istest(x,GIT_GLOB_SPECIAL)
 #define is_regex_special(x) sane_istest(x,GIT_GLOB_SPECIAL | GIT_REGEX_SPECIAL)
 #define tolower(x) sane_case((unsigned char)(x), 0x20)
@@ -491,6 +495,17 @@ static inline int sane_case(int x, int high)
 	return x;
 }
 
+static inline int sane_iscase(int x, int is_lower)
+{
+	if (!sane_istest(x, GIT_ALPHA))
+		return 0;
+
+	if (is_lower)
+		return (x & 0x20) != 0;
+	else
+		return (x & 0x20) == 0;
+}
+
 static inline int strtoul_ui(char const *s, int base, unsigned int *result)
 {
 	unsigned long ul;