git-send-email: avoid duplicate message-ids

We used to unconditionally add a message-id to the outgoing
email without bothering to check if it already had one.
Instead, let's use the existing one.

Signed-off-by: Jeff King <peff@peff.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

diff --git a/git-send-email.perl b/git-send-email.perl
index b03297c9d7ed40f39b9f805c08bf9c2f17bb7379..e8354c760be11eec7c0b74b62aeaf4ec95a85d91 100755 (executable)
--- a/git-send-email.perl
+++ b/git-send-email.perl
@@ -527,7 +527,7 @@ sub send_message
                $ccline = "\nCc: $cc";
        }
        my $sanitized_sender = sanitize_address($sender);
-       make_message_id();
+       make_message_id() unless defined($message_id);
 
        my $header = "From: $sanitized_sender
 To: $to${ccline}
@@ -643,6 +643,9 @@ foreach my $t (@files) {
                                        }
                                        push @xh, $_;
                                }
+                               elsif (/^Message-Id: (.*)/i) {
+                                       $message_id = $1;
+                               }
                                elsif (!/^Date:\s/ && /^[-A-Za-z]+:\s+\S/) {
                                        push @xh, $_;
                                }
@@ -728,6 +731,7 @@ foreach my $t (@files) {
                        $references = "$message_id";
                }
        }
+       $message_id = undef;
 }
 
 if ($compose) {