lei: fix `-c NAME=VALUE' config support

We can pass `-c NAME=VALUE' args directly to git-config without
needing a temporary directory nor file.  Furthermore, this opens
the door to us being able to correctly handle `-c NAME=VALUE'
after `delete $lei->{cfg}' if we need to reload the config
during a command.

This tightens up error-checking for `lei config' and ensures we
can make config settings changes while using `-c NAME=VALUE'
instead of editing the temporary file.

The non-obvious part was avoiding the use of the -f/--file arg for
`git config' for read-only operations and include relying on
`-c include.path=$ABS_PATH'.  This is done by parsing the
switches to be passed to `git config' to determine if it's a
read-only operation or not.

1 files changed, 41 insertions, 11 deletions

diff --git a/lib/PublicInbox/Config.pm b/lib/PublicInbox/Config.pm
index f6236d84..533f4a52 100644
--- a/lib/PublicInbox/Config.pm
+++ b/lib/PublicInbox/Config.pm
@@ -22,7 +22,7 @@ sub _array ($) { ref($_[0]) eq 'ARRAY' ? $_[0] : [ $_[0] ] }
 # returns key-value pairs of config directives in a hash
 # if keys may be multi-value, the value is an array ref containing all values
 sub new {
-        my ($class, $file, $errfh) = @_;
+        my ($class, $file, $lei) = @_;
         $file //= default_file();
         my $self;
         my $set_dedupe;
@@ -36,7 +36,7 @@ sub new {
                         $self = $DEDUPE->{$file} and return $self;
                         $set_dedupe = 1;
                 }
-                $self = git_config_dump($class, $file, $errfh);
+                $self = git_config_dump($class, $file, $lei);
                 $self->{'-f'} = $file;
         }
         # caches
@@ -174,13 +174,34 @@ sub config_fh_parse ($$$) {
         \%rv;
 }
 
+sub tmp_cmd_opt ($$) {
+        my ($env, $opt) = @_;
+        # quiet global and system gitconfig if supported by installed git,
+        # but normally harmless if too noisy (NOGLOBAL no longer exists)
+        $env->{GIT_CONFIG_NOSYSTEM} = 1;
+        $env->{GIT_CONFIG_GLOBAL} = '/dev/null'; # git v2.32+
+        $opt->{-C} = '/'; # avoid $worktree/.git/config on MOST systems :P
+}
+
 sub git_config_dump {
-        my ($class, $file, $errfh) = @_;
-        return bless {}, $class unless -e $file;
-        my $cmd = [ qw(git config -z -l --includes), "--file=$file" ];
-        my $fh = popen_rd($cmd, undef, { 2 => $errfh // 2 });
+        my ($class, $file, $lei) = @_;
+        my @opt_c = map { ('-c', $_) } @{$lei->{opt}->{c} // []};
+        $file = undef if !-e $file;
+        # XXX should we set {-f} if !-e $file?
+        return bless {}, $class if (!@opt_c && !defined($file));
+        my %env;
+        my $opt = { 2 => $lei->{2} // 2 };
+        if (@opt_c) {
+                unshift(@opt_c, '-c', "include.path=$file") if defined($file);
+                tmp_cmd_opt(\%env, $opt);
+        }
+        my @cmd = ('git', @opt_c, qw(config -z -l --includes));
+        push(@cmd, '-f', $file) if !@opt_c && defined($file);
+        my $fh = popen_rd(\@cmd, \%env, $opt);
         my $rv = config_fh_parse($fh, "\0", "\n");
-        close $fh or die "@$cmd failed: \$?=$?\n";
+        close $fh or die "@cmd failed: \$?=$?\n";
+        $rv->{-opt_c} = \@opt_c if @opt_c; # for ->urlmatch
+        $rv->{-f} = $file;
         bless $rv, $class;
 }
 
@@ -544,14 +565,23 @@ sub _fill_ei ($$) {
         $es;
 }
 
+sub config_cmd {
+        my ($self, $env, $opt) = @_;
+        my $f = $self->{-f} // default_file();
+        my @opt_c = @{$self->{-opt_c} // []};
+        my @cmd = ('git', @opt_c, 'config');
+        @opt_c ? tmp_cmd_opt($env, $opt) : push(@cmd, '-f', $f);
+        \@cmd;
+}
+
 sub urlmatch {
         my ($self, $key, $url, $try_git) = @_;
         state $urlmatch_broken; # requires git 1.8.5
         return if $urlmatch_broken;
-        my $file = $self->{'-f'} // default_file();
-        my $cmd = [qw/git config -z --includes --get-urlmatch/,
-                "--file=$file", $key, $url ];
-        my $fh = popen_rd($cmd);
+        my (%env, %opt);
+        my $cmd = $self->config_cmd(\%env, \%opt);
+        push @$cmd, qw(-z --includes --get-urlmatch), $key, $url;
+        my $fh = popen_rd($cmd, \%env, \%opt);
         local $/ = "\0";
         my $val = <$fh>;
         if (!close($fh)) {