* Get garbage collection and cache population to work *properly*.

  Renamed `fstateRefs' to `fstateRequisites'.  The semantics of this
  function is that it returns a list of all paths necessary to realise
  a given expression.  For a derive expression, this is the union of
  requisites of the inputs; for a slice expression, it is the path of
  each element in the slice.  Also included are the paths of the
  expressions themselves.  Optionally, one can also include the
  requisites of successor expressions (to recycle intermediate
  results).

* `nix-switch' now distinguishes between an expression and its normal
  form.  Usually, only the normal form is registered as a root of the
  garbage collector.  With the `--source-root' flag, it will also
  register the original expression as a root.

* `nix-collect-garbage' now has a flag `--keep-successors' which
  causes successors not to be included in the list of garbage paths.

* `nix-collect-garbage' now has a flag `--invert' which will print all
  paths that should *not* be garbage collected.

1 files changed, 15 insertions, 1 deletions

diff --git a/scripts/nix-collect-garbage.in b/scripts/nix-collect-garbage.in
index 8f54ba20f3e4..eaa706578117 100755
--- a/scripts/nix-collect-garbage.in
+++ b/scripts/nix-collect-garbage.in
@@ -5,13 +5,27 @@ my $storedir = "@prefix@/store";
 
 my %alive;
 
-open HASHES, "nix --query --refs \$(cat $linkdir/*.hash) |" or die "in `nix -qrh'";
+my $keepsuccessors = 0;
+my $invert = 0;
+
+foreach my $arg (@ARGV) {
+    if ($arg eq "--keep-successors") { $keepsuccessors = 1; }
+    if ($arg eq "--invert") { $invert = 1; }
+    else { die "unknown argument `$arg'" };
+}
+
+my $extraarg = "";
+if ($keepsuccessors) { $extraarg = "--include-successors"; };
+open HASHES, "nix --query --requisites $extraarg \$(cat $linkdir/*.id) |" or die "in `nix -qrh'";
 while (<HASHES>) {
 	chomp;
 	$alive{$_} = 1;
+	if ($invert) { print "$_\n"; };
 }
 close HASHES;
 
+exit 0 if ($invert);
+
 opendir(DIR, $storedir) or die "cannot opendir $storedir: $!";
 my @names = readdir(DIR);
 closedir DIR;