Merge branch 'nd/icase'

"git grep -i" has been taught to fold case in non-ascii locales
correctly.

* nd/icase:
  grep.c: reuse "icase" variable
  diffcore-pickaxe: support case insensitive match on non-ascii
  diffcore-pickaxe: Add regcomp_or_die()
  grep/pcre: support utf-8
  gettext: add is_utf8_locale()
  grep/pcre: prepare locale-dependent tables for icase matching
  grep: rewrite an if/else condition to avoid duplicate expression
  grep/icase: avoid kwsset when -F is specified
  grep/icase: avoid kwsset on literal non-ascii strings
  test-regex: expose full regcomp() to the command line
  test-regex: isolate the bug test code
  grep: break down an "if" stmt in preparation for next changes

t/helper/test-regex.c

@@ -1,6 +1,23 @@
 #include "git-compat-util.h"
+#include "gettext.h"
 
-int main(int argc, char **argv)
+struct reg_flag {
+	const char *name;
+	int flag;
+};
+
+static struct reg_flag reg_flags[] = {
+	{ "EXTENDED",	 REG_EXTENDED	},
+	{ "NEWLINE",	 REG_NEWLINE	},
+	{ "ICASE",	 REG_ICASE	},
+	{ "NOTBOL",	 REG_NOTBOL	},
+#ifdef REG_STARTEND
+	{ "STARTEND",	 REG_STARTEND	},
+#endif
+	{ NULL, 0 }
+};
+
+static int test_regex_bug(void)
 {
 	char *pat = "[^={} \t]+";
 	char *str = "={}\nfred";
@@ -16,5 +33,43 @@ int main(int argc, char **argv)
 	if (m[0].rm_so == 3) /* matches '\n' when it should not */
 		die("regex bug confirmed: re-build git with NO_REGEX=1");
 
-	exit(0);
+	return 0;
+}
+
+int main(int argc, char **argv)
+{
+	const char *pat;
+	const char *str;
+	int flags = 0;
+	regex_t r;
+	regmatch_t m[1];
+
+	if (argc == 2 && !strcmp(argv[1], "--bug"))
+		return test_regex_bug();
+	else if (argc < 3)
+		usage("test-regex --bug\n"
+		      "test-regex <pattern> <string> [<options>]");
+
+	argv++;
+	pat = *argv++;
+	str = *argv++;
+	while (*argv) {
+		struct reg_flag *rf;
+		for (rf = reg_flags; rf->name; rf++)
+			if (!strcmp(*argv, rf->name)) {
+				flags |= rf->flag;
+				break;
+			}
+		if (!rf->name)
+			die("do not recognize %s", *argv);
+		argv++;
+	}
+	git_setup_gettext();
+
+	if (regcomp(&r, pat, flags))
+		die("failed regcomp() for pattern '%s'", pat);
+	if (regexec(&r, str, 1, m, 0))
+		return 1;
+
+	return 0;
 }