checkpatch: allow space leading blank lines in email headers

Allow a leading space and otherwise blank link in the email headers as
it can be a line wrapped Spamassassin multiple line string or any other
valid rfc 2822/5322 email header.

The line with space causes checkpatch to erroneously think that it's in
the content body, as opposed to headers and thus flag a mail header as
an unwrapped long comment line.

Link: http://lkml.kernel.org/r/d75a9f0b78b3488078429f4037d9fff3bdfa3b78.1490247180.git.joe@perches.com
Signed-off-by: Joe Perches <joe@perches.com>Reported-by: Darren Hart (VMware) <dvhart@infradead.org>
Tested-by: Darren Hart (VMware) <dvhart@infradead.org>
Reviewed-by: Darren Hart (VMware) <dvhart@vmware.com>
Original-patch-by: John 'Warthog9' Hawley (VMware) <warthog9@eaglescrag.net>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

scripts/checkpatch.pl

@@ -2628,8 +2628,8 @@ 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 =~ /^\s+\S/ ||
-		      $rawline =~ /^(commit\b|from\b|[\w-]+:).*$/i)) {
+		    !($rawline =~ /^\s+(?:\S|$)/ ||
+		      $rawline =~ /^(?:commit\b|from\b|[\w-]+:)/i)) {
 			$in_header_lines = 0;
 			$in_commit_log = 1;
 			$has_commit_log = 1;