cleanup: add isascii()

Add a standard definition of isascii() and use it to replace an open
coded high-bit test in pretty.c.  While we're there, write the ESC
char as the more commonly used '\033' instead of as 0x1b to enhance
its grepability.

Signed-off-by: Rene Scharfe <rene.scharfe@lsrfire.ath.cx>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

git-compat-util.h

@@ -319,6 +319,7 @@ static inline int has_extension(const char *filename, const char *ext)
 }
 
 /* Sane ctype - no locale, and works with signed chars */
+#undef isascii
 #undef isspace
 #undef isdigit
 #undef isalpha
@@ -332,6 +333,7 @@ extern unsigned char sane_ctype[256];
 #define GIT_GLOB_SPECIAL 0x08
 #define GIT_REGEX_SPECIAL 0x10
 #define sane_istest(x,mask) ((sane_ctype[(unsigned char)(x)] & (mask)) != 0)
+#define isascii(x) (((x) & ~0x7f) == 0)
 #define isspace(x) sane_istest(x,GIT_SPACE)
 #define isdigit(x) sane_istest(x,GIT_DIGIT)
 #define isalpha(x) sane_istest(x,GIT_ALPHA)

pretty.c

@@ -75,8 +75,7 @@ static int get_one_line(const char *msg)
 /* High bit set, or ISO-2022-INT */
 int non_ascii(int ch)
 {
-	ch = (ch & 0xff);
-	return ((ch & 0x80) || (ch == 0x1b));
+	return !isascii(ch) || ch == '\033';
 }
 
 static int is_rfc2047_special(char ch)