grep/pcre: prepare locale-dependent tables for icase matching

The default tables are usually built with C locale and only suitable
for LANG=C or similar.  This should make case insensitive search work
correctly for all single-byte charsets.

Signed-off-by: Nguyễn Thái Ngọc Duy <pclouds@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

grep.c

@@ -324,11 +324,14 @@ static void compile_pcre_regexp(struct grep_pat *p, const struct grep_opt *opt)
 	int erroffset;
 	int options = PCRE_MULTILINE;
 
-	if (opt->ignore_case)
+	if (opt->ignore_case) {
+		if (has_non_ascii(p->pattern))
+			p->pcre_tables = pcre_maketables();
 		options |= PCRE_CASELESS;
+	}
 
 	p->pcre_regexp = pcre_compile(p->pattern, options, &error, &erroffset,
-			NULL);
+				      p->pcre_tables);
 	if (!p->pcre_regexp)
 		compile_regexp_failed(p, error);
 
@@ -362,6 +365,7 @@ static void free_pcre_regexp(struct grep_pat *p)
 {
 	pcre_free(p->pcre_regexp);
 	pcre_free(p->pcre_extra_info);
+	pcre_free((void *)p->pcre_tables);
 }
 #else /* !USE_LIBPCRE */
 static void compile_pcre_regexp(struct grep_pat *p, const struct grep_opt *opt)

grep.h

@@ -48,6 +48,7 @@ struct grep_pat {
 	regex_t regexp;
 	pcre *pcre_regexp;
 	pcre_extra *pcre_extra_info;
+	const unsigned char *pcre_tables;
 	kwset_t kws;
 	unsigned fixed:1;
 	unsigned ignore_case:1;

t/t7813-grep-icase-iso.sh

@@ -0,0 +1,19 @@
+#!/bin/sh
+
+test_description='grep icase on non-English locales'
+
+. ./lib-gettext.sh
+
+test_expect_success GETTEXT_ISO_LOCALE 'setup' '
+	printf "TILRAUN: Halló Heimur!" >file &&
+	git add file &&
+	LC_ALL="$is_IS_iso_locale" &&
+	export LC_ALL
+'
+
+test_expect_success GETTEXT_ISO_LOCALE,LIBPCRE 'grep pcre string' '
+	git grep --perl-regexp -i "TILRAUN: H.lló Heimur!" &&
+	git grep --perl-regexp -i "TILRAUN: H.LLÓ HEIMUR!"
+'
+
+test_done