send-email: expose header information to git-send-email's sendemail-validate hook

To allow further flexibility in the Git hook, the SMTP header
information of the email which git-send-email intends to send, is now
passed as the 2nd argument to the sendemail-validate hook.

As an example, this can be useful for acting upon keywords in the
subject or specific email addresses.

Cc: Luben Tuikov <luben.tuikov@amd.com>
Cc: Junio C Hamano <gitster@pobox.com>
Cc: Ævar Arnfjörð Bjarmason <avarab@gmail.com>
Acked-by: Luben Tuikov <luben.tuikov@amd.com>
Signed-off-by: Michael Strawbridge <michael.strawbridge@amd.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

Author: Michael Strawbridge

Documentation/githooks.txt

@@ -595,10 +595,29 @@ processed by rebase.
 sendemail-validate
 ~~~~~~~~~~~~~~~~~~
 
-This hook is invoked by linkgit:git-send-email[1].  It takes a single parameter,
-the name of the file that holds the e-mail to be sent.  Exiting with a
-non-zero status causes `git send-email` to abort before sending any
-e-mails.
+This hook is invoked by linkgit:git-send-email[1].
+
+It takes these command line arguments. They are,
+1. the name of the file which holds the contents of the email to be sent.
+2. The name of the file which holds the SMTP headers of the email.
+
+The SMTP headers are passed in the exact same way as they are passed to the
+user's Mail Transport Agent (MTA). In effect, the email given to the user's
+MTA, is the contents of $2 followed by the contents of $1.
+
+An example of a few common headers is shown below. Take notice of the
+capitalization and multi-line tab structure.
+
+  From: Example <from@example.com>
+  To: to@example.com
+  Cc: cc@example.com,
+	  A <author@example.com>,
+	  One <one@example.com>,
+	  two@example.com
+  Subject: PATCH-STRING
+
+Exiting with a non-zero status causes `git send-email` to abort
+before sending any e-mails.
 
 fsmonitor-watchman
 ~~~~~~~~~~~~~~~~~~

git-send-email.perl

@@ -792,16 +792,31 @@ sub is_format_patch_arg {
 				    @rev_list_opts);
 }
 
-@files = handle_backup_files(@files);
+if (defined $sender) {
+	$sender =~ s/^\s+|\s+$//g;
+	($sender) = expand_aliases($sender);
+} else {
+	$sender = $repoauthor->() || $repocommitter->() || '';
+}
+
+# $sender could be an already sanitized address
+# (e.g. sendemail.from could be manually sanitized by user).
+# But it's a no-op to run sanitize_address on an already sanitized address.
+$sender = sanitize_address($sender);
+
+$time = time - scalar $#files;
 
 if ($validate) {
 	foreach my $f (@files) {
 		unless (-p $f) {
+		        pre_process_file($f, 1);
 			validate_patch($f, $target_xfer_encoding);
 		}
 	}
 }
 
+@files = handle_backup_files(@files);
+
 if (@files) {
 	unless ($quiet) {
 		print $_,"\n" for (@files);
@@ -1050,18 +1065,6 @@ sub file_declares_8bit_cte {
 	}
 }
 
-if (defined $sender) {
-	$sender =~ s/^\s+|\s+$//g;
-	($sender) = expand_aliases($sender);
-} else {
-	$sender = $repoauthor->() || $repocommitter->() || '';
-}
-
-# $sender could be an already sanitized address
-# (e.g. sendemail.from could be manually sanitized by user).
-# But it's a no-op to run sanitize_address on an already sanitized address.
-$sender = sanitize_address($sender);
-
 my $to_whom = __("To whom should the emails be sent (if anyone)?");
 my $prompting = 0;
 if (!@initial_to && !defined $to_cmd) {
@@ -1221,10 +1224,6 @@ sub make_message_id {
 	#print "new message id = $message_id\n"; # Was useful for debugging
 }
 
-
-
-$time = time - scalar $#files;
-
 sub unquote_rfc2047 {
 	local ($_) = @_;
 	my $charset;
@@ -2108,10 +2107,21 @@ sub validate_patch {
 			chdir($repo->wc_path() or $repo->repo_path())
 				or die("chdir: $!");
 			local $ENV{"GIT_DIR"} = $repo->repo_path();
+
+			my ($recipients_ref, $to, $date, $gitversion, $cc, $ccline, $header) = gen_header();
+
+			require File::Temp;
+			my ($header_filehandle, $header_filename) = File::Temp::tempfile(
+                            TEMPLATE => ".gitsendemail.header.XXXXXX",
+                            DIR => $repo->repo_path(),
+                            UNLINK => 1,
+                        );
+			print $header_filehandle $header;
+
 			my @cmd = ("git", "hook", "run", "--ignore-missing",
 				    $hook_name, "--");
-			my @cmd_msg = (@cmd, "<patch>");
-			my @cmd_run = (@cmd, $target);
+			my @cmd_msg = (@cmd, "<patch>", "<header>");
+			my @cmd_run = (@cmd, $target, $header_filename);
 			$hook_error = system_or_msg(\@cmd_run, undef, "@cmd_msg");
 			chdir($cwd_save) or die("chdir: $!");
 		}

t/t9001-send-email.sh

@@ -540,7 +540,7 @@ test_expect_success $PREREQ "--validate respects relative core.hooksPath path" '
 	test_path_is_file my-hooks.ran &&
 	cat >expect <<-EOF &&
 	fatal: longline.patch: rejected by sendemail-validate hook
-	fatal: command '"'"'git hook run --ignore-missing sendemail-validate -- <patch>'"'"' died with exit code 1
+	fatal: command '"'"'git hook run --ignore-missing sendemail-validate -- <patch> <header>'"'"' died with exit code 1
 	warning: no patches were sent
 	EOF
 	test_cmp expect actual
@@ -559,12 +559,35 @@ test_expect_success $PREREQ "--validate respects absolute core.hooksPath path" '
 	test_path_is_file my-hooks.ran &&
 	cat >expect <<-EOF &&
 	fatal: longline.patch: rejected by sendemail-validate hook
-	fatal: command '"'"'git hook run --ignore-missing sendemail-validate -- <patch>'"'"' died with exit code 1
+	fatal: command '"'"'git hook run --ignore-missing sendemail-validate -- <patch> <header>'"'"' died with exit code 1
 	warning: no patches were sent
 	EOF
 	test_cmp expect actual
 '
 
+test_expect_success $PREREQ "--validate hook supports header argument" '
+	write_script my-hooks/sendemail-validate <<-\EOF &&
+	if test "$#" -ge 2
+	then
+		grep "X-test-header: v1.0" "$2"
+	else
+		echo "No header arg passed"
+		exit 1
+	fi
+	EOF
+	test_config core.hooksPath "my-hooks" &&
+	rm -fr outdir &&
+	git format-patch \
+		--add-header="X-test-header: v1.0" \
+		-n HEAD^1 -o outdir &&
+	git send-email \
+		--dry-run \
+		--to=nobody@example.com \
+		--smtp-server="$(pwd)/fake.sendmail" \
+		--validate \
+		outdir/000?-*.patch
+'
+
 for enc in 7bit 8bit quoted-printable base64
 do
 	test_expect_success $PREREQ "--transfer-encoding=$enc produces correct header" '