www_coderepo: /tree/ 404s search git history

Displaying git trees over the web with pathnames in the URLs
have the unfortunate consequence of URLs getting out-of-date
if files are renamed or deleted from the latest tree.

We can utilize `git log' here to search history and find the
commit which led to the rename or deletion.  Of course, we'll
show a suitable command to the user as well, another small
step towards covertly teaching users the git CLI :>

`git log' is not especially fast, here, but Qspawn limiters can
do their job and renames and deletions aren't too common in most
codebases.

1 files changed, 42 insertions, 1 deletions

diff --git a/lib/PublicInbox/RepoTree.pm b/lib/PublicInbox/RepoTree.pm
index 7f2ff206..cec71eb6 100644
--- a/lib/PublicInbox/RepoTree.pm
+++ b/lib/PublicInbox/RepoTree.pm
@@ -7,11 +7,51 @@ use v5.12;
 use PublicInbox::ViewDiff qw(uri_escape_path);
 use PublicInbox::GitAsyncCat;
 use PublicInbox::WwwStatic qw(r);
+use PublicInbox::Qspawn;
+use PublicInbox::WwwStream qw(html_oneshot);
+use PublicInbox::Hval qw(ascii_html);
+
+sub rd_404_log {
+        my ($bref, $ctx) = @_;
+        my $path = $ctx->{-q_value_html} = ascii_html($ctx->{-path});
+        my $tip = 'HEAD';
+        $tip = ascii_html($ctx->{qp}->{h}) if defined($ctx->{qp}->{h});
+        PublicInbox::WwwStream::html_init($ctx);
+        my $zfh = $ctx->{zfh};
+        print $zfh "<pre>\$ git log -1 $tip -- $path\n";
+        if ($$bref eq '') {
+                say $zfh "found no record of `$path' in git history";
+                $ctx->{-has_srch} and
+                        say $zfh 'perhaps try searching mail (above)';
+        } else {
+                my ($H, $h, $s_as) = split(/ /, $$bref, 3);
+                utf8::decode($s_as);
+                my $x = uri_escape_path($ctx->{-path});
+                $s_as = ascii_html($s_as);
+                print $zfh <<EOM;
+found last record of `$path' in the following commit:
+
+<a href="$ctx->{-upfx}$H/s/?b=$x">$h</a> $s_as
+EOM
+        }
+        delete($ctx->{-wcb})->($ctx->html_done);
+}
+
+sub find_missing {
+        my ($ctx) = @_;
+        my $cmd = ['git', "--git-dir=$ctx->{git}->{git_dir}",
+                qw(log --no-color -1), '--pretty=%H %h %s (%as)' ];
+        push @$cmd, $ctx->{qp}->{h} if defined($ctx->{qp}->{h});
+        push @$cmd, '--';
+        push @$cmd, $ctx->{-path} if $ctx->{-path} ne '';
+        my $qsp = PublicInbox::Qspawn->new($cmd);
+        $qsp->psgi_qx($ctx->{env}, undef, \&rd_404_log, $ctx);
+}
 
 sub tree_30x { # git check_async callback
         my ($oid, $type, $size, $ctx) = @_;
+        return find_missing($ctx) if $type eq 'missing';
         my $wcb = delete $ctx->{-wcb};
-        return $wcb->(r(404)) if $type eq 'missing';
         my $u = $ctx->{git}->base_url($ctx->{env});
         my $path = uri_escape_path(delete $ctx->{-path});
         $u .= "$oid/s/?b=$path";
@@ -23,6 +63,7 @@ sub srv_tree {
         my ($ctx, $path) = @_;
         return if index($path, '//') >= 0 || index($path, '/') == 0;
         my $tip = $ctx->{qp}->{h} // 'HEAD';
+        $ctx->{-upfx} = '../' x (($path =~ tr!/!/!) + 1);
         $path =~ s!/\z!!;
         my $obj = $ctx->{-obj} = "$tip:$path";
         $ctx->{-path} = $path;