config: reject `\n' in `inboxdir'

"\n" and other characters requiring quoting and/or escaping in
in $GIT_DIR/objects/info/alternates was not supported in git 2.11
and earlier; nor does it seem supported at all in libgit2.

This will allow us to support sharing git-cat-file or similar
endpoints across multiple inboxes via alternates.

This breaks an existing use case for anybody wacky
enough to put `\n' in the `inboxdir' pathname; but I doubt
this affects anybody.

1 files changed, 4 insertions, 1 deletions

diff --git a/lib/PublicInbox/Config.pm b/lib/PublicInbox/Config.pm
index c0e2cc57..67199bb3 100644
--- a/lib/PublicInbox/Config.pm
+++ b/lib/PublicInbox/Config.pm
@@ -393,7 +393,10 @@ sub _fill {
 
         # backwards compatibility:
         $ibx->{inboxdir} //= $self->{"$pfx.mainrepo"};
-
+        if (($ibx->{inboxdir} // '') =~ /\n/s) {
+                warn "E: `$ibx->{inboxdir}' must not contain `\\n'\n";
+                return;
+        }
         foreach my $k (qw(obfuscate)) {
                 my $v = $self->{"$pfx.$k"};
                 defined $v or next;