From ba92106e93c66e41af5180ac1b6ad0f959f72bb4 Mon Sep 17 00:00:00 2001
From: Maxim Cournoyer <maxim.cournoyer@gmail.com>
Date: Mon, 1 May 2023 10:38:47 -0400
Subject: send-email: add --header-cmd, --no-header-cmd options

Sometimes, adding a header different than CC or TO is desirable; for
example, when using Debbugs, it is best to use 'X-Debbugs-Cc' headers
to keep people in CC; this is an example use case enabled by the new
'--header-cmd' option.

The header unfolding logic is extracted to a subroutine so that it can
be reused; a test is added for coverage.

Signed-off-by: Maxim Cournoyer <maxim.cournoyer@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
---
 git-send-email.perl | 55 +++++++++++++++++++++++++++++++++++++++++------------
 1 file changed, 43 insertions(+), 12 deletions(-)

(limited to 'git-send-email.perl')

diff --git a/git-send-email.perl b/git-send-email.perl
index 04503e3c3c..32febe9af3 100755
--- a/git-send-email.perl
+++ b/git-send-email.perl
@@ -87,8 +87,10 @@ git send-email --dump-aliases
 
   Automating:
     --identity              <str>  * Use the sendemail.<id> options.
-    --to-cmd                <str>  * Email To: via `<str> \$patch_path`
-    --cc-cmd                <str>  * Email Cc: via `<str> \$patch_path`
+    --to-cmd                <str>  * Email To: via `<str> \$patch_path`.
+    --cc-cmd                <str>  * Email Cc: via `<str> \$patch_path`.
+    --header-cmd            <str>  * Add headers via `<str> \$patch_path`.
+    --no-header-cmd                * Disable any header command in use.
     --suppress-cc           <str>  * author, self, sob, cc, cccmd, body, bodycc, misc-by, all.
     --[no-]cc-cover                * Email Cc: addresses in the cover letter.
     --[no-]to-cover                * Email To: addresses in the cover letter.
@@ -202,7 +204,7 @@ my (@to,@cc,@xh,$envelope_sender,
 	$author,$sender,$smtp_authpass,$annotate,$compose,$time);
 # Things we either get from config, *or* are overridden on the
 # command-line.
-my ($no_cc, $no_to, $no_bcc, $no_identity);
+my ($no_cc, $no_to, $no_bcc, $no_identity, $no_header_cmd);
 my (@config_to, @getopt_to);
 my (@config_cc, @getopt_cc);
 my (@config_bcc, @getopt_bcc);
@@ -269,7 +271,7 @@ sub do_edit {
 # Variables with corresponding config settings
 my ($suppress_from, $signed_off_by_cc);
 my ($cover_cc, $cover_to);
-my ($to_cmd, $cc_cmd);
+my ($to_cmd, $cc_cmd, $header_cmd);
 my ($smtp_server, $smtp_server_port, @smtp_server_options);
 my ($smtp_authuser, $smtp_encryption, $smtp_ssl_cert_path);
 my ($batch_size, $relogin_delay);
@@ -318,6 +320,7 @@ my %config_settings = (
     "tocmd" => \$to_cmd,
     "cc" => \@config_cc,
     "cccmd" => \$cc_cmd,
+    "headercmd" => \$header_cmd,
     "aliasfiletype" => \$aliasfiletype,
     "bcc" => \@config_bcc,
     "suppresscc" => \@suppress_cc,
@@ -519,6 +522,8 @@ my %options = (
 		    "compose" => \$compose,
 		    "quiet" => \$quiet,
 		    "cc-cmd=s" => \$cc_cmd,
+		    "header-cmd=s" => \$header_cmd,
+		    "no-header-cmd" => \$no_header_cmd,
 		    "suppress-from!" => \$suppress_from,
 		    "no-suppress-from" => sub {$suppress_from = 0},
 		    "suppress-cc=s" => \@suppress_cc,
@@ -1780,16 +1785,16 @@ sub process_file {
 	$subject = $initial_subject;
 	$message = "";
 	$message_num++;
-	# First unfold multiline header fields
+	# Retrieve and unfold header fields.
+	my @header_lines = ();
 	while(<$fh>) {
 		last if /^\s*$/;
-		if (/^\s+\S/ and @header) {
-			chomp($header[$#header]);
-			s/^\s+/ /;
-			$header[$#header] .= $_;
-	    } else {
-			push(@header, $_);
-		}
+		push(@header_lines, $_);
+	}
+	@header = unfold_headers(@header_lines);
+	# Add computed headers, if applicable.
+	unless ($no_header_cmd || ! $header_cmd) {
+		push @header, invoke_header_cmd($header_cmd, $t);
 	}
 	# Now parse the header
 	foreach(@header) {
@@ -2036,6 +2041,32 @@ sub execute_cmd {
 	return @lines;
 }
 
+# Process headers lines, unfolding multiline headers as defined by RFC
+# 2822.
+sub unfold_headers {
+	my @headers;
+	foreach(@_) {
+		last if /^\s*$/;
+		if (/^\s+\S/ and @headers) {
+			chomp($headers[$#headers]);
+			s/^\s+/ /;
+			$headers[$#headers] .= $_;
+		} else {
+			push(@headers, $_);
+		}
+	}
+	return @headers;
+}
+
+# Invoke the provided CMD with FILE as an argument, which should
+# output RFC 2822 email headers. Fold multiline headers and return the
+# headers as an array.
+sub invoke_header_cmd {
+	my ($cmd, $file) = @_;
+	my @lines = execute_cmd("header-cmd", $header_cmd, $file);
+	return unfold_headers(@lines);
+}
+
 # Execute a command (e.g. $to_cmd) to get a list of email addresses
 # and return a results array
 sub recipients_cmd {
-- 
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