lei: fix git-credential handling

I completely forgot about git-credential prompting when
making lei background the client process for MUA.

Now it backgrounds itself only for the MUA when no FDs are
passed, since the MUA is the final command run.  Otherwise, it
relies on FD passing as before.

Fixes: c790a75439f3a1db ("script/lei: background ourselves on MUA/pager exec")

2 files changed, 38 insertions, 16 deletions

diff --git a/lib/PublicInbox/LEI.pm b/lib/PublicInbox/LEI.pm
index 69d48bd1..f9361c68 100644
--- a/lib/PublicInbox/LEI.pm
+++ b/lib/PublicInbox/LEI.pm
@@ -839,7 +839,13 @@ sub start_mua {
         if (my $sock = $self->{sock}) { # lei(1) client process runs it
                 send($sock, exec_buf(\@cmd, {}), MSG_EOR);
         } elsif ($self->{oneshot}) {
-                $self->{"pid.$self.$$"}->{spawn(\@cmd)} = \@cmd;
+                my $pid = fork // die "fork: $!";
+                if ($pid > 0) { # original process
+                        exec(@cmd);
+                        warn "exec @cmd: $!\n";
+                        POSIX::_exit(1);
+                }
+                POSIX::setsid() > 0 or die "setsid: $!";
         }
         if ($self->{lxs} && $self->{au_done}) { # kick wait_startq
                 syswrite($self->{au_done}, 'q' x ($self->{lxs}->{jobs} // 0));
diff --git a/script/lei b/script/lei
index bea8dcde..78a7dab9 100755
--- a/script/lei
+++ b/script/lei
@@ -14,31 +14,45 @@ my $send_cmd = PublicInbox::CmdIPC4->can('send_cmd4') // do {
         PublicInbox::Spawn->can('send_cmd4');
 };
 
-my @orig_pid;
+my %pids;
+my $sigchld = sub {
+        my $flags = scalar(@_) ? POSIX::WNOHANG() : 0;
+        for my $pid (keys %pids) {
+                delete($pids{$pid}) if waitpid($pid, $flags) == $pid;
+        }
+};
+my @parent;
 my $exec_cmd = sub {
         my ($fds, $argc, @argv) = @_;
-        die "BUG: already exec-ed\n" if @orig_pid;
-        @orig_pid = ($$);
-        require POSIX; # WNOHANG
+        my $parent = $$;
+        require POSIX;
         my @old = (*STDIN{IO}, *STDOUT{IO}, *STDERR{IO});
         my @rdr;
         for my $fd (@$fds) {
-                open(my $tmpfh, '+<&=', $fd) or die "open +<&=$fd: $!";
-                push @rdr, shift(@old), $tmpfh;
+                open(my $newfh, '+<&=', $fd) or die "open +<&=$fd: $!";
+                push @rdr, shift(@old), $newfh;
         }
+        my $do_exec = sub {
+                my %env = map { split(/=/, $_, 2) } splice(@argv, $argc);
+                @ENV{keys %env} = values %env;
+                exec(@argv);
+                warn "exec: @argv: $!\n";
+                POSIX::_exit(1);
+        };
+        $SIG{CHLD} = $sigchld;
         my $pid = fork // die "fork: $!";
         if ($pid == 0) {
+                while (my ($io, $newfh) = splice(@rdr, 0, 2)) {
+                        open $io, '+<&', $newfh or die "open +<&=: $!";
+                }
+                $do_exec->() if scalar(@$fds); # git-credential, pager
+
+                # parent backgrounds on MUA
                 POSIX::setsid() > 0 or die "setsid: $!";
+                @parent = ($parent);
                 return; # continue $recv_cmd in background
         }
-        my %env = map { split(/=/, $_, 2) } splice(@argv, $argc);
-        while (my ($old_io, $tmpfh) = splice(@rdr, 0, 2)) {
-                open $old_io, '+<&', $tmpfh or die "open +<&=: $!";
-        }
-        @ENV{keys %env} = values %env;
-        exec(@argv);
-        warn "exec: @argv: $!\n";
-        POSIX::_exit(1);
+        $do_exec->() if !scalar(@$fds); # MUA reuses all FDs
 };
 
 if ($send_cmd && eval {
@@ -95,16 +109,18 @@ Falling back to (slow) one-shot mode
                 if ($buf =~ /\Aexec (.+)\z/) {
                         $exec_cmd->(\@fds, split(/\0/, $1));
                 } elsif ($buf eq '-WINCH') {
-                        kill($buf, @orig_pid); # for MUA
+                        kill($buf, @parent); # for MUA
                 } elsif ($buf =~ /\Ax_it ([0-9]+)\z/) {
                         $x_it_code = $1 + 0;
                         last;
                 } elsif ($buf =~ /\Achild_error ([0-9]+)\z/) {
                         $x_it_code = $1 + 0;
                 } else {
+                        $sigchld->();
                         die $buf;
                 }
         }
+        $sigchld->();
         if (my $sig = ($x_it_code & 127)) {
                 kill $sig, $$;
                 sleep(1) while 1;