[PATCH v4 04/10] grep/icase: avoid kwsset on literal non-ascii strings

["Nguyễn Thái Ngọc Duy" <pclouds@gmail.com>]

When we detect the pattern is just a literal string, we avoid heavy
regex engine and use fast substring search implemented in kwsset.c.
But kws uses git-ctype which is locale-independent so it does not know
how to fold case properly outside ascii range. Let regcomp or pcre
take care of this case instead. Slower, but accurate.

Helped-by: René Scharfe <l.s.r@web.de>
Noticed-by: Plamen Totev <plamen.totev@abv.bg>
Signed-off-by: Nguyễn Thái Ngọc Duy <pclouds@gmail.com>
---
 grep.c                                   |  7 ++++++-
 t/t7812-grep-icase-non-ascii.sh (new +x) | 23 +++++++++++++++++++++++
 2 files changed, 29 insertions(+), 1 deletion(-)
 create mode 100755 t/t7812-grep-icase-non-ascii.sh

diff --git a/grep.c b/grep.c
index bd32f66..d795b0e 100644
--- a/grep.c
+++ b/grep.c
@@ -4,6 +4,7 @@
 #include "xdiff-interface.h"
 #include "diff.h"
 #include "diffcore.h"
+#include "commit.h"
 
 static int grep_source_load(struct grep_source *gs);
 static int grep_source_is_binary(struct grep_source *gs);
@@ -398,12 +399,16 @@ static int is_fixed(const char *s, size_t len)
 
 static void compile_regexp(struct grep_pat *p, struct grep_opt *opt)
 {
+	int icase_non_ascii;
 	int err;
 
 	p->word_regexp = opt->word_regexp;
 	p->ignore_case = opt->ignore_case;
+	icase_non_ascii =
+		(opt->regflags & REG_ICASE || p->ignore_case) &&
+		has_non_ascii(p->pattern);
 
-	if (is_fixed(p->pattern, p->patternlen))
+	if (!icase_non_ascii && is_fixed(p->pattern, p->patternlen))
 		p->fixed = 1;
 	else if (opt->fixed) {
 		p->fixed = 1;
diff --git a/t/t7812-grep-icase-non-ascii.sh b/t/t7812-grep-icase-non-ascii.sh
new file mode 100755
index 0000000..6eff490
--- /dev/null
+++ b/t/t7812-grep-icase-non-ascii.sh
@@ -0,0 +1,23 @@
+#!/bin/sh
+
+test_description='grep icase on non-English locales'
+
+. ./lib-gettext.sh
+
+test_expect_success GETTEXT_LOCALE 'setup' '
+	printf "TILRAUN: Halló Heimur!" >file &&
+	git add file &&
+	LC_ALL="$is_IS_locale" &&
+	export LC_ALL
+'
+
+test_have_prereq GETTEXT_LOCALE &&
+test-regex "HALLÓ" "Halló" ICASE &&
+test_set_prereq REGEX_LOCALE
+
+test_expect_success REGEX_LOCALE 'grep literal string, no -F' '
+	git grep -i "TILRAUN: Halló Heimur!" &&
+	git grep -i "TILRAUN: HALLÓ HEIMUR!"
+'
+
+test_done
-- 
2.3.0.rc1.137.g477eb31