mailinfo: allow stripping quoted CR without warning

In previous changes, we've turned on warning for quoted CR in base64 or
quoted-printable email messages. Some projects see those quoted CR a lot,
they know that it happens most of the time, and they find it's desirable
to always strip those CR.

Those projects in question usually fall back to use other tools to handle
patches when receive such patches.

Let's help those projects handle those patches by stripping those
excessive CR.

Signed-off-by: Đoàn Trần Công Danh <congdanhqx@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

Documentation/git-mailinfo.txt

@@ -102,6 +102,7 @@ The valid actions are:
 *	`nowarn`: Git will do nothing when such a CRLF is found.
 *	`warn`: Git will issue a warning for each message if such a CRLF is
 	found.
+*	`strip`: Git will convert those CRLF to LF.
 --
 +
 The default action could be set by configuration option `mailinfo.quotedCR`.

mailinfo.c

@@ -998,6 +998,11 @@ static void handle_filter_flowed(struct mailinfo *mi, struct strbuf *line,
 		    line->buf[len - 2] == '\r' &&
 		    line->buf[len - 1] == '\n') {
 			mi->have_quoted_cr = 1;
+			if (mi->quoted_cr == quoted_cr_strip) {
+				strbuf_setlen(line, len - 2);
+				strbuf_addch(line, '\n');
+				len--;
+			}
 		}
 		handle_filter(mi, line);
 		return;
@@ -1227,6 +1232,8 @@ int mailinfo_parse_quoted_cr_action(const char *actionstr, int *action)
 		*action = quoted_cr_nowarn;
 	else if (!strcmp(actionstr, "warn"))
 		*action = quoted_cr_warn;
+	else if (!strcmp(actionstr, "strip"))
+		*action = quoted_cr_strip;
 	else
 		return -1;
 	return 0;

mailinfo.h

@@ -8,6 +8,7 @@
 enum quoted_cr_action {
 	quoted_cr_nowarn,
 	quoted_cr_warn,
+	quoted_cr_strip,
 };
 
 struct mailinfo {

t/t5100-mailinfo.sh

@@ -259,6 +259,12 @@ test_expect_success 'mailinfo warn CR in base64 encoded email' '
 	check_quoted_cr_mail quoted-cr/0001 --quoted-cr=nowarn &&
 	test_must_be_empty quoted-cr/0001.err &&
 	check_quoted_cr_mail quoted-cr/0002 --quoted-cr=nowarn &&
+	test_must_be_empty quoted-cr/0002.err &&
+	cp quoted-cr/0001-expected.msg quoted-cr/0002-expected.msg &&
+	cp quoted-cr/0001-expected.patch quoted-cr/0002-expected.patch &&
+	check_quoted_cr_mail quoted-cr/0001 --quoted-cr=strip &&
+	test_must_be_empty quoted-cr/0001.err &&
+	check_quoted_cr_mail quoted-cr/0002 --quoted-cr=strip &&
 	test_must_be_empty quoted-cr/0002.err
 '