am: fix patch format detection for Thunderbird "Save As" emails

The patch detection wants to inspect all the headers of a rfc2822 message
and ensure that they look like header fields. The headers are always
separated from the message body with a blank line. When Thunderbird saves
the message the blank line separating the headers from the body includes a
CR. The patch detection is failing because a CRLF doesn't match /^$/. Fix
this by allowing a CR to exist on the separating line.

Signed-off-by: Stephen Boyd <bebarino@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

git-am.sh

@@ -205,7 +205,8 @@ check_patch_format () {
 			# discarding the indented remainder of folded lines,
 			# and see if it looks like that they all begin with the
 			# header field names...
-			sed -n -e '/^$/q' -e '/^[ 	]/d' -e p "$1" |
+			tr -d '\015' <"$1" |
+			sed -n -e '/^$/q' -e '/^[ 	]/d' -e p |
 			sane_egrep -v '^[!-9;-~]+:' >/dev/null ||
 			patch_format=mbox
 		fi

t/t4150-am.sh

@@ -83,6 +83,12 @@ test_expect_success setup '
 		echo "X-Fake-Field: Line Three" &&
 		git format-patch --stdout first | sed -e "1d"
 	} > patch1.eml &&
+	{
+		echo "X-Fake-Field: Line One" &&
+		echo "X-Fake-Field: Line Two" &&
+		echo "X-Fake-Field: Line Three" &&
+		git format-patch --stdout first | sed -e "1d"
+	} | append_cr >patch1-crlf.eml &&
 	sed -n -e "3,\$p" msg >file &&
 	git add file &&
 	test_tick &&
@@ -123,6 +129,15 @@ test_expect_success 'am applies patch e-mail not in a mbox' '
 	test "$(git rev-parse second^)" = "$(git rev-parse HEAD^)"
 '
 
+test_expect_success 'am applies patch e-mail not in a mbox with CRLF' '
+	git checkout first &&
+	git am patch1-crlf.eml &&
+	! test -d .git/rebase-apply &&
+	test -z "$(git diff second)" &&
+	test "$(git rev-parse second)" = "$(git rev-parse HEAD)" &&
+	test "$(git rev-parse second^)" = "$(git rev-parse HEAD^)"
+'
+
 GIT_AUTHOR_NAME="Another Thor"
 GIT_AUTHOR_EMAIL="a.thor@example.com"
 GIT_COMMITTER_NAME="Co M Miter"