Merge branch 'ag/send-email-outlook' into jch

Update send-email to work better with Outlook's smtp server.

* ag/send-email-outlook:
  send-email: add --[no-]outlook-id-fix option
  send-email: retrieve Message-ID from outlook SMTP server

Documentation/git-send-email.adoc

@@ -115,6 +115,19 @@ illustration below where `[PATCH v2 0/3]` is in reply to `[PATCH 0/2]`:
 Only necessary if --compose is also set.  If --compose
 is not set, this will be prompted for.
 
+--[no-]outlook-id-fix::
+	Microsoft Outlook SMTP servers discard the Message-ID sent via email and
+	assign a new random Message-ID, thus breaking threads.
++
+With `--outlook-id-fix`, 'git send-email' uses a mechanism specific to
+Outlook servers to learn the Message-ID the server assigned to fix the
+threading. Use it only when you know that the server reports the
+rewritten Message-ID the same way as Outlook servers do.
++
+Without this option specified, the fix is done by default when talking
+to 'smtp.office365.com' or 'smtp-mail.outlook.com'. Use
+`--no-outlook-id-fix` to disable even when talking to these two servers.
+
 --subject=<string>::
 	Specify the initial subject of the email thread.
 	Only necessary if --compose is also set.  If --compose

git-send-email.perl

@@ -41,6 +41,8 @@ git send-email --translate-aliases
     --subject               <str>  * Email "Subject:"
     --reply-to              <str>  * Email "Reply-To:"
     --in-reply-to           <str>  * Email "In-Reply-To:"
+    --[no-]outlook-id-fix          * The SMTP host is an Outlook server that munges the
+                                     Message-ID. Retrieve it from the server.
     --[no-]xmailer                 * Add "X-Mailer:" header (default).
     --[no-]annotate                * Review each patch that will be sent in an editor.
     --compose                      * Open an editor for introduction.
@@ -68,7 +70,7 @@ git send-email --translate-aliases
     --smtp-auth             <str>  * Space-separated list of allowed AUTH mechanisms, or
                                      "none" to disable authentication.
                                      This setting forces to use one of the listed mechanisms.
-    --no-smtp-auth                   Disable SMTP authentication. Shorthand for
+    --no-smtp-auth                 * Disable SMTP authentication. Shorthand for
                                      `--smtp-auth=none`
     --smtp-debug            <0|1>  * Disable, enable Net::SMTP debug.
 
@@ -290,6 +292,7 @@ my $validate = 1;
 my $mailmap = 0;
 my $target_xfer_encoding = 'auto';
 my $forbid_sendmail_variables = 1;
+my $outlook_id_fix = 'auto';
 
 my %config_bool_settings = (
     "thread" => \$thread,
@@ -305,6 +308,7 @@ my %config_bool_settings = (
     "xmailer" => \$use_xmailer,
     "forbidsendmailvariables" => \$forbid_sendmail_variables,
     "mailmap" => \$mailmap,
+    "outlookidfix" => \$outlook_id_fix,
 );
 
 my %config_settings = (
@@ -551,6 +555,7 @@ my %options = (
 		    "relogin-delay=i" => \$relogin_delay,
 		    "git-completion-helper" => \$git_completion_helper,
 		    "v=s" => \$reroll_count,
+		    "outlook-id-fix!" => \$outlook_id_fix,
 );
 $rc = GetOptions(%options);
 
@@ -1574,6 +1579,16 @@ Message-ID: $message_id
 	return ($recipients_ref, $to, $date, $gitversion, $cc, $ccline, $header);
 }
 
+sub is_outlook {
+	my ($host) = @_;
+	if ($outlook_id_fix eq 'auto') {
+		$outlook_id_fix =
+			($host eq 'smtp.office365.com' ||
+			 $host eq 'smtp-mail.outlook.com') ? 1 : 0;
+	}
+	return $outlook_id_fix;
+}
+
 # Prepares the email, then asks the user what to do.
 #
 # If the user chooses to send the email, it's sent and 1 is returned.
@@ -1737,6 +1752,22 @@ EOF
 			$smtp->datasend("$line") or die $smtp->message;
 		}
 		$smtp->dataend() or die $smtp->message;
+
+		# Outlook discards the Message-ID header we set while sending the email
+		# and generates a new random Message-ID. So in order to avoid breaking
+		# threads, we simply retrieve the Message-ID from the server response
+		# and assign it to the $message_id variable, which will then be
+		# assigned to $in_reply_to by the caller when the next message is sent
+		# as a response to this message.
+		if (is_outlook($smtp_server)) {
+			if ($smtp->message =~ /<([^>]+)>/) {
+				$message_id = "<$1>";
+				printf __("Outlook reassigned Message-ID to: %s\n"), $message_id;
+			} else {
+				warn __("Warning: Could not retrieve Message-ID from server response.\n");
+			}
+		}
+
 		$smtp->code =~ /250|200/ or die sprintf(__("Failed to send %s\n"), $subject).$smtp->message;
 	}
 	if ($quiet) {