-# abs_path resolves symlinks, so we want to avoid it if rel2abs
-# is sufficient and doesn't leave "/.." or "/../"
-sub rel2abs_collapsed ($) {
- my $p = File::Spec->rel2abs($_[0]);
- return $p if substr($p, -3, 3) ne '/..' && index($p, '/../') < 0; # likely
- require Cwd;
- Cwd::abs_path($p);
+sub resolve_eidxdir {
+ my ($cd) = @_;
+ my $try = $cd // '.';
+ my $root_dev_ino;
+ while (1) { # favor v2, first
+ if (-f "$try/ei.lock") {
+ return rel2abs_collapsed($try);
+ } elsif (-d $try) {
+ my @try = stat _;
+ $root_dev_ino //= do {
+ my @root = stat('/') or die "stat /: $!\n";
+ "$root[0]\0$root[1]";
+ };
+ return undef if "$try[0]\0$try[1]" eq $root_dev_ino;
+ $try .= '/..'; # continue, cd up
+ } else {
+ die "`$try' is not a directory\n";
+ }
+ }