fetch: ignore non-writable epoch dirs

This will eventually be useful for maintaing partial mirrors.

Keeping inline with the original public-inbox-fetch philosophy,
there are no additional config files to manage:
the user merely needs to remove write permissions to an $N.git
directory to prevent it from being updated.

Re-enabling updates just requires restoring write permission.

1 files changed, 15 insertions, 4 deletions

diff --git a/lib/PublicInbox/Fetch.pm b/lib/PublicInbox/Fetch.pm
index 993e5b19..0bd6502c 100644
--- a/lib/PublicInbox/Fetch.pm
+++ b/lib/PublicInbox/Fetch.pm
@@ -96,7 +96,7 @@ sub do_fetch { # main entry point
         my $ibx_ver;
         $lei->{curl} //= PublicInbox::LeiCurl->new($lei) or return;
         my $dir = PublicInbox::Admin::resolve_inboxdir($cd, \$ibx_ver);
-        my ($ibx_uri, @git_dir, @epochs, $mg, @new_epoch);
+        my ($ibx_uri, @git_dir, @epochs, $mg, @new_epoch, $skip);
         if ($ibx_ver == 1) {
                 my $url = remote_url($lei, $dir) //
                         die "E: $dir missing remote.origin.url\n";
@@ -108,6 +108,10 @@ sub do_fetch { # main entry point
                 my ($git_url, $epoch);
                 for my $nr (@epochs) { # try newest epoch, first
                         my $edir = "$dir/git/$nr.git";
+                        unless (-d $edir && -w _) { # must be writable dir
+                                $skip->{$nr} = 1;
+                                next;
+                        }
                         if (defined(my $url = remote_url($lei, $edir))) {
                                 $git_url = $url;
                                 $epoch = $nr;
@@ -116,6 +120,8 @@ sub do_fetch { # main entry point
                                 warn "W: $edir missing remote.origin.url\n";
                         }
                 }
+                @epochs = grep { !$skip->{$_} } @epochs if $skip;
+                $skip //= {}; # makes code below easier
                 $git_url or die "Unable to determine git URL\n";
                 my $inbox_url = $git_url;
                 $inbox_url =~ s!/git/$epoch(?:\.git)?/?\z!! or
@@ -132,7 +138,10 @@ EOM
                 # any pre-manifest.js.gz instances running? Just fetch all
                 # existing ones and unconditionally try cloning the next
                 $v2_epochs = [ map { "$dir/git/$_.git" } @epochs ];
-                push @$v2_epochs, "$dir/git/".($epochs[-1] + 1) if @epochs;
+                if (@epochs) {
+                        my $n = $epochs[-1] + 1;
+                        push @$v2_epochs, "$dir/git/$n.git" if !$skip->{$n};
+                }
         } else {
                 $code == 200 or die "BUG unexpected code $code\n";
         }
@@ -140,8 +149,10 @@ EOM
                 defined($v1_path) and warn <<EOM;
 E: got v1 `$v1_path' when expecting v2 epoch(s) in <$muri>, WTF?
 EOM
-                @git_dir = map { "$dir/git/$_.git" } sort { $a <=> $b }
-                        map { my ($nr) = (m!/([0-9]+)\.git\z!g) } @$v2_epochs;
+                @git_dir = map { "$dir/git/$_.git" } sort { $a <=> $b } map {
+                                my ($nr) = (m!/([0-9]+)\.git\z!g);
+                                $skip->{$nr} ? () : $nr;
+                        } @$v2_epochs;
         } else {
                 $git_dir[0] = $dir;
         }