send-email: don't cc *-by lines with '-' prefix

Since commit ef0cc1d ("send-email: also pick up cc addresses from
-by trailers") in git version 2.20, git send-email adds to cc list
addresses from all *-by lines. As a side effect a line with
'-Signed-off-by' is now also added to cc. This makes send-email pick
lines from patches that remove patch files from the git repo. This is
common in the Buildroot project that often removes (and adds) patch
files that have 'Signed-off-by' in their patch description part.

Consider only *-by lines that start with [a-z] (case insensitive) to
avoid unrelated addresses in cc.

Cc: Joe Perches <[email protected]>
Signed-off-by: Baruch Siach <[email protected]>
Acked-by: Rasmus Villemoes <[email protected]>
Signed-off-by: Junio C Hamano <[email protected]>

Author: baruchsiach

git-send-email.perl

@@ -1699,7 +1699,7 @@ sub process_file {
 	# Now parse the message body
 	while(<$fh>) {
 		$message .=  $_;
-		if (/^([a-z-]*-by|Cc): (.*)/i) {
+		if (/^([a-z][a-z-]*-by|Cc): (.*)/i) {
 			chomp;
 			my ($what, $c) = ($1, $2);
 			# strip garbage for the address we'll use: