[PATCH 2/2] send-email: add --header-cmd option

[Maxim Cournoyer <maxim.cournoyer@gmail.com>]

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.
---
 Documentation/config/sendemail.txt |  1 +
 Documentation/git-send-email.txt   |  5 +++++
 git-send-email.perl                | 12 +++++++++---
 t/t9001-send-email.sh              | 21 +++++++++++++++++++--
 4 files changed, 34 insertions(+), 5 deletions(-)

diff --git a/Documentation/config/sendemail.txt b/Documentation/config/sendemail.txt
index 51da7088a8..3d0f516520 100644
--- a/Documentation/config/sendemail.txt
+++ b/Documentation/config/sendemail.txt
@@ -58,6 +58,7 @@ sendemail.annotate::
 sendemail.bcc::
 sendemail.cc::
 sendemail.ccCmd::
+sendemail.headerCmd::
 sendemail.chainReplyTo::
 sendemail.envelopeSender::
 sendemail.from::
diff --git a/Documentation/git-send-email.txt b/Documentation/git-send-email.txt
index b0f438ec99..354c0d06db 100644
--- a/Documentation/git-send-email.txt
+++ b/Documentation/git-send-email.txt
@@ -320,6 +320,11 @@ Automating
 	Output of this command must be single email address per line.
 	Default is the value of `sendemail.ccCmd` configuration value.
 
+--header-cmd=<command>::
+	Specify a command to execute once per patch file which should
+	generate arbitrary, patch file specific header entries.
+	Default is the value of `sendemail.headerCmd` configuration value.
+
 --[no-]chain-reply-to::
 	If this is set, each email will be sent as a reply to the previous
 	email sent.  If disabled with "--no-chain-reply-to", all emails after
diff --git a/git-send-email.perl b/git-send-email.perl
index d2febbda1f..676dd83d89 100755
--- a/git-send-email.perl
+++ b/git-send-email.perl
@@ -88,8 +88,9 @@ sub usage {
 
   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`.
     --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.
@@ -270,7 +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, $relogin_delay);
@@ -319,6 +320,7 @@ sub do_edit {
     "tocmd" => \$to_cmd,
     "cc" => \@config_cc,
     "cccmd" => \$cc_cmd,
+    "headercmd" => \$header_cmd,
     "aliasfiletype" => \$aliasfiletype,
     "bcc" => \@config_bcc,
     "suppresscc" => \@suppress_cc,
@@ -520,6 +522,7 @@ sub config_regexp {
 		    "compose" => \$compose,
 		    "quiet" => \$quiet,
 		    "cc-cmd=s" => \$cc_cmd,
+		    "header-cmd=s" => \$header_cmd,
 		    "suppress-from!" => \$suppress_from,
 		    "no-suppress-from" => sub {$suppress_from = 0},
 		    "suppress-cc=s" => \@suppress_cc,
@@ -1777,6 +1780,9 @@ sub process_file {
 			push(@header, $_);
 		}
 	}
+	# Add computed headers, if applicable.
+	push @header, execute_cmd("header-cmd", $header_cmd, $t)
+		if defined $header_cmd;
 	# Now parse the header
 	foreach(@header) {
 		if (/^From /) {
diff --git a/t/t9001-send-email.sh b/t/t9001-send-email.sh
index 0de83b5d2b..3393725107 100755
--- a/t/t9001-send-email.sh
+++ b/t/t9001-send-email.sh
@@ -374,13 +374,16 @@ test_expect_success $PREREQ,!AUTOIDENT 'broken implicit ident aborts send-email'
 	)
 '
 
-test_expect_success $PREREQ 'setup tocmd and cccmd scripts' '
+test_expect_success $PREREQ 'setup cmd scripts' '
 	write_script tocmd-sed <<-\EOF &&
 	sed -n -e "s/^tocmd--//p" "$1"
 	EOF
-	write_script cccmd-sed <<-\EOF
+	write_script cccmd-sed <<-\EOF &&
 	sed -n -e "s/^cccmd--//p" "$1"
 	EOF
+	write_script headercmd-sed <<-\EOF
+	sed -n -e "s/^headercmd--//p" "$1"
+	EOF
 '
 
 test_expect_success $PREREQ 'tocmd works' '
@@ -410,6 +413,20 @@ test_expect_success $PREREQ 'cccmd works' '
 	grep "^	cccmd@example.com" msgtxt1
 '
 
+test_expect_success $PREREQ 'headercmd works' '
+	clean_fake_sendmail &&
+	cp $patches headercmd.patch &&
+	echo "headercmd--X-Debbugs-CC: dummy@example.com" >>headercmd.patch &&
+	git send-email \
+		--from="Example <nobody@example.com>" \
+		--to=nobody@example.com \
+		--header-cmd=./headercmd-sed \
+		--smtp-server="$(pwd)/fake.sendmail" \
+		headercmd.patch \
+		&&
+	grep "^X-Debbugs-CC: dummy@example.com" msgtxt1
+'
+
 test_expect_success $PREREQ 'reject long lines' '
 	z8=zzzzzzzz &&
 	z64=$z8$z8$z8$z8$z8$z8$z8$z8 &&
-- 
2.39.2