[PATCH v3 10/13] send-email: lazily load modules for a big speedup

["Ævar Arnfjörð Bjarmason" <avarab@gmail.com>]

Optimize the time git-send-email takes to do even the simplest of
things (such as serving up "-h") from around ~150ms to ~80ms-~90ms by
lazily loading the modules it requires.

Before this change Devel::TraceUse would report 99/97 used modules
under NO_GETTEXT=[|Y], respectively. Now it's 52/37. It now takes ~15s
to run t9001-send-email.sh, down from ~20s.

Signed-off-by: Ævar Arnfjörð Bjarmason <avarab@gmail.com>
---
 git-send-email.perl | 71 +++++++++++++++++++++++++--------------------
 1 file changed, 39 insertions(+), 32 deletions(-)

diff --git a/git-send-email.perl b/git-send-email.perl
index f1542cb3ea..1e9273fd4f 100755
--- a/git-send-email.perl
+++ b/git-send-email.perl
@@ -19,20 +19,10 @@
 use 5.008;
 use strict;
 use warnings $ENV{GIT_PERL_FATAL_WARNINGS} ? qw(FATAL all) : ();
-use POSIX qw/strftime/;
-use Term::ReadLine;
 use Getopt::Long;
-use Text::ParseWords;
-use Term::ANSIColor;
-use File::Temp qw/ tempdir tempfile /;
-use File::Spec::Functions qw(catdir catfile);
 use Git::LoadCPAN::Error qw(:try);
-use Cwd qw(abs_path cwd);
 use Git;
 use Git::I18N;
-use Net::Domain ();
-use Net::SMTP ();
-use Git::LoadCPAN::Mail::Address;
 
 Getopt::Long::Configure qw/ pass_through /;
 
@@ -166,7 +156,6 @@ sub format_2822_time {
 		       );
 }
 
-my $have_email_valid = eval { require Email::Valid; 1 };
 my $smtp;
 my $auth;
 my $num_sent = 0;
@@ -192,14 +181,6 @@ sub format_2822_time {
 
 my $repo = eval { Git->repository() };
 my @repo = $repo ? ($repo) : ();
-my $term = eval {
-	$ENV{"GIT_SEND_EMAIL_NOTTY"}
-		? Term::ReadLine->new('git-send-email', \*STDIN, \*STDOUT)
-		: Term::ReadLine->new('git-send-email');
-};
-if ($@) {
-	$term = FakeTerm->new("$@: going non-interactive");
-}
 
 # Behavior modification variables
 my ($quiet, $dry_run) = (0, 0);
@@ -309,9 +290,9 @@ sub do_edit {
 
 # Handle Uncouth Termination
 sub signal_handler {
-
 	# Make text normal
-	print color("reset"), "\n";
+	require Term::ANSIColor;
+	print Term::ANSIColor::color("reset"), "\n";
 
 	# SMTP password masked
 	system "stty echo";
@@ -592,11 +573,13 @@ sub config_regexp {
 }
 
 sub parse_address_line {
+	require Git::LoadCPAN::Mail::Address;
 	return map { $_->format } Mail::Address->parse($_[0]);
 }
 
 sub split_addrs {
-	return quotewords('\s*,\s*', 1, @_);
+	require Text::ParseWords;
+	return Text::ParseWords::quotewords('\s*,\s*', 1, @_);
 }
 
 my %aliases;
@@ -645,10 +628,11 @@ sub parse_sendmail_aliases {
 			s/\\"/"/g foreach @addr;
 			$aliases{$alias} = \@addr
 		}}},
-	mailrc => sub { my $fh = shift; while (<$fh>) {
+	mailrc => sub {	my $fh = shift; while (<$fh>) {
 		if (/^alias\s+(\S+)\s+(.*?)\s*$/) {
+			require Text::ParseWords;
 			# spaces delimit multiple addresses
-			$aliases{$1} = [ quotewords('\s+', 0, $2) ];
+			$aliases{$1} = [ Text::ParseWords::quotewords('\s+', 0, $2) ];
 		}}},
 	pine => sub { my $fh = shift; my $f='\t[^\t]*';
 	        for (my $x = ''; defined($x); $x = $_) {
@@ -720,7 +704,8 @@ sub is_format_patch_arg {
 		opendir my $dh, $f
 			or die sprintf(__("Failed to opendir %s: %s"), $f, $!);
 
-		push @files, grep { -f $_ } map { catfile($f, $_) }
+		require File::Spec;
+		push @files, grep { -f $_ } map { File::Spec->catfile($f, $_) }
 				sort readdir $dh;
 		closedir $dh;
 	} elsif ((-f $f or -p $f) and !is_format_patch_arg($f)) {
@@ -733,7 +718,8 @@ sub is_format_patch_arg {
 if (@rev_list_opts) {
 	die __("Cannot run git format-patch from outside a repository\n")
 		unless $repo;
-	push @files, $repo->command('format-patch', '-o', tempdir(CLEANUP => 1), @rev_list_opts);
+	require File::Temp;
+	push @files, $repo->command('format-patch', '-o', File::Temp::tempdir(CLEANUP => 1), @rev_list_opts);
 }
 
 @files = handle_backup_files(@files);
@@ -770,9 +756,10 @@ sub get_patch_subject {
 if ($compose) {
 	# Note that this does not need to be secure, but we will make a small
 	# effort to have it be unique
+	require File::Temp;
 	$compose_filename = ($repo ?
-		tempfile(".gitsendemail.msg.XXXXXX", DIR => $repo->repo_path()) :
-		tempfile(".gitsendemail.msg.XXXXXX", DIR => "."))[1];
+		File::Temp::tempfile(".gitsendemail.msg.XXXXXX", DIR => $repo->repo_path()) :
+		File::Temp::tempfile(".gitsendemail.msg.XXXXXX", DIR => "."))[1];
 	open my $c, ">", $compose_filename
 		or die sprintf(__("Failed to open for writing %s: %s"), $compose_filename, $!);
 
@@ -879,6 +866,19 @@ sub get_patch_subject {
 	do_edit(@files);
 }
 
+sub term {
+	my $term = eval {
+		require Term::ReadLine;
+		$ENV{"GIT_SEND_EMAIL_NOTTY"}
+			? Term::ReadLine->new('git-send-email', \*STDIN, \*STDOUT)
+			: Term::ReadLine->new('git-send-email');
+	};
+	if ($@) {
+		$term = FakeTerm->new("$@: going non-interactive");
+	}
+	return $term;
+}
+
 sub ask {
 	my ($prompt, %arg) = @_;
 	my $valid_re = $arg{valid_re};
@@ -886,6 +886,7 @@ sub ask {
 	my $confirm_only = $arg{confirm_only};
 	my $resp;
 	my $i = 0;
+	my $term = term();
 	return defined $default ? $default : undef
 		unless defined $term->IN and defined fileno($term->IN) and
 		       defined $term->OUT and defined fileno($term->OUT);
@@ -1066,6 +1067,7 @@ sub extract_valid_address {
 	return $address if ($address =~ /^($local_part_regexp)$/);
 
 	$address =~ s/^\s*<(.*)>\s*$/$1/;
+	my $have_email_valid = eval { require Email::Valid; 1 };
 	if ($have_email_valid) {
 		return scalar Email::Valid->address($address);
 	}
@@ -1125,7 +1127,8 @@ sub validate_address_list {
 sub make_message_id {
 	my $uniq;
 	if (!defined $message_id_stamp) {
-		$message_id_stamp = strftime("%Y%m%d%H%M%S.$$", gmtime(time));
+		require POSIX;
+		$message_id_stamp = POSIX::strftime("%Y%m%d%H%M%S.$$", gmtime(time));
 		$message_id_serial = 0;
 	}
 	$message_id_serial++;
@@ -1295,6 +1298,7 @@ sub valid_fqdn {
 sub maildomain_net {
 	my $maildomain;
 
+	require Net::Domain;
 	my $domain = Net::Domain::domainname();
 	$maildomain = $domain if valid_fqdn($domain);
 
@@ -1305,6 +1309,7 @@ sub maildomain_mta {
 	my $maildomain;
 
 	for my $host (qw(mailhost localhost)) {
+		require Net::SMTP;
 		my $smtp = Net::SMTP->new($host);
 		if (defined $smtp) {
 			my $domain = $smtp->domain;
@@ -1983,13 +1988,15 @@ sub validate_patch {
 	my ($fn, $xfer_encoding) = @_;
 
 	if ($repo) {
-		my $validate_hook = catfile($repo->hooks_path(),
+		require File::Spec;
+		my $validate_hook = File::Spec->catfile($repo->hooks_path(),
 					    'sendemail-validate');
 		my $hook_error;
 		if (-x $validate_hook) {
-			my $target = abs_path($fn);
+			require Cwd;
+			my $target = Cwd::abs_path($fn);
 			# The hook needs a correct cwd and GIT_DIR.
-			my $cwd_save = cwd();
+			my $cwd_save = Cwd::cwd();
 			chdir($repo->wc_path() or $repo->repo_path())
 				or die("chdir: $!");
 			local $ENV{"GIT_DIR"} = $repo->repo_path();
-- 
2.32.0.rc0.406.g05cb3eebfc