grep/icase: avoid kwsset when -F is specified

Similar to the previous commit, we can't use kws on icase search
outside ascii range. But we can't simply pass the pattern to
regcomp/pcre like the previous commit because it may contain regex
special characters, so we need to quote the regex first.

To avoid misquote traps that could lead to undefined behavior, we
always stick to basic regex engine in this case. We don't need fancy
features for grepping a literal string anyway.

basic_regex_quote_buf() assumes that if the pattern is in a multibyte
encoding, ascii chars must be unambiguously encoded as single
bytes. This is true at least for UTF-8. For others, let's wait until
people yell up. Chances are nobody uses multibyte, non utf-8 charsets
anymore.

Noticed-by: Plamen Totev <plamen.totev@abv.bg>
Helped-by: René Scharfe <l.s.r@web.de>
Helped-by: Eric Sunshine <sunshine@sunshineco.com>
Signed-off-by: Nguyễn Thái Ngọc Duy <pclouds@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

1 files changed, 37 insertions, 0 deletions

diff --git a/quote.c b/quote.c
index fe884d245..c67adb718 100644
--- a/quote.c
+++ b/quote.c
@@ -440,3 +440,40 @@ void tcl_quote_buf(struct strbuf *sb, const char *src)
 	}
 	strbuf_addch(sb, '"');
 }
+
+void basic_regex_quote_buf(struct strbuf *sb, const char *src)
+{
+	char c;
+
+	if (*src == '^') {
+		/* only beginning '^' is special and needs quoting */
+		strbuf_addch(sb, '\\');
+		strbuf_addch(sb, *src++);
+	}
+	if (*src == '*')
+		/* beginning '*' is not special, no quoting */
+		strbuf_addch(sb, *src++);
+
+	while ((c = *src++)) {
+		switch (c) {
+		case '[':
+		case '.':
+		case '\\':
+		case '*':
+			strbuf_addch(sb, '\\');
+			strbuf_addch(sb, c);
+			break;
+
+		case '$':
+			/* only the end '$' is special and needs quoting */
+			if (*src == '\0')
+				strbuf_addch(sb, '\\');
+			strbuf_addch(sb, c);
+			break;
+
+		default:
+			strbuf_addch(sb, c);
+			break;
+		}
+	}
+}