checkpatch: ignore email headers better

There are some patches created by git format-patch that when scanned by
checkpatch report errors on lines like

To:	address.tld

This is a checkpatch false positive.

Improve the logic a bit to ignore folded email headers to avoid emitting
these messages.

Signed-off-by: Joe Perches <joe@perches.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Reviewed-by: Markus Armbruster <armbru@redhat.com>
Reviewed-by: Thomas Huth <thuth@redhat.com>
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
Message-id: 20180430124651.10340-4-stefanha@redhat.com
(cherry picked from commit 29ee1b0c67e0dd7dea8dd718e8326076bce5b6fe)
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
Reviewed-by: Thomas Huth <thuth@redhat.com>
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>

scripts/checkpatch.pl

@@ -1183,7 +1183,7 @@ sub process {
 	my $signoff = 0;
 	my $is_patch = 0;
 
-	my $in_header_lines = 1;
+	my $in_header_lines = $file ? 0 : 1;
 	my $in_commit_log = 0;		#Scanning lines before patch
 
 	my $non_utf8_charset = 0;
@@ -1411,7 +1411,8 @@ sub process {
 # Check if it's the start of a commit log
 # (not a header line and we haven't seen the patch filename)
 		if ($in_header_lines && $realfile =~ /^$/ &&
-		    $rawline !~ /^(commit\b|from\b|\w+:).+$/i) {
+		    !($rawline =~ /^\s+\S/ ||
+		      $rawline =~ /^(commit\b|from\b|[\w-]+:).*$/i)) {
 			$in_header_lines = 0;
 			$in_commit_log = 1;
 		}