* 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, 35 insertions, 17 deletions

diff --git a/scripts/nix-switch.in b/scripts/nix-switch.in
index ddaca4e22..db0e96f3e 100755
--- a/scripts/nix-switch.in
+++ b/scripts/nix-switch.in
@@ -3,39 +3,56 @@
 use strict;
 
 my $keep = 0;
-
-if (scalar @ARGV > 0 && $ARGV[0] eq "--keep") {
-    shift @ARGV;
-    $keep = 1;
+my $sourceroot = 0;
+my $srcid;
+
+foreach my $arg (@ARGV) {
+    if ($arg eq "--keep") { $keep = 1; }
+    elsif ($arg eq "--source-root") { $sourceroot = 1; }
+    elsif ($arg =~ /^([0-9a-z]{32})$/) { $srcid = $arg; }
+    else { die "unknown argument `$arg'" };
 }
 
-my $hash = $ARGV[0];
-$hash || die "no package hash specified";
-
 my $linkdir = "@localstatedir@/nix/links";
 
 # Build the specified package, and all its dependencies.
-system "nix --install $hash";
+my $nfid = `nix --install $srcid`;
 if ($?) { die "`nix --install' failed"; }
+chomp $nfid;
+die unless $nfid =~ /^([0-9a-z]{32})$/;
 
-my $pkgdir = `nix --query --list $hash`;
+my $pkgdir = `nix --query --list $nfid`;
 if ($?) { die "`nix --query --list' failed"; }
 chomp $pkgdir;
 
 # Figure out a generation number.
+opendir(DIR, $linkdir);
 my $nr = 0;
-while (-e "$linkdir/$nr") { $nr++; }
+foreach my $n (sort(readdir(DIR))) {
+    next if (!($n =~ /^\d+$/));
+    $nr = $n + 1 if ($n >= $nr);
+}
+closedir(DIR);
+
 my $link = "$linkdir/$nr";
 
 # Create a symlink from $link to $pkgdir.
 symlink($pkgdir, $link) or die "cannot create $link: $!";
 
-# Also store the hash of $pkgdir.  This is useful for garbage
+# Store the id of the normal form.  This is useful for garbage
 # collection and the like.
-my $hashfile = "$linkdir/$nr.hash";
-open HASH, "> $hashfile" or die "cannot create $hashfile";
-print HASH "$hash\n";
-close HASH;
+my $idfile = "$linkdir/$nr.id";
+open ID, "> $idfile" or die "cannot create $idfile";
+print ID "$nfid\n";
+close ID;
+
+# Optionally store the source id.
+if ($sourceroot) {
+    $idfile = "$linkdir/$nr-src.id";
+    open ID, "> $idfile" or die "cannot create $idfile";
+    print ID "$srcid\n";
+    close ID;
+}
 
 my $current = "$linkdir/current";
 
@@ -59,6 +76,7 @@ rename($tmplink, $current) or die "cannot rename $tmplink";
 
 if (!$keep && defined $oldlink) {
     print "deleting old $oldlink\n";
-    unlink($oldlink) == 1 || print "cannot delete $oldlink\n";
-    unlink("$oldlink.hash") == 1 || print "cannot delete $oldlink.hash\n";
+    unlink($oldlink) == 1 or print "cannot delete $oldlink\n";
+    unlink("$oldlink.id") == 1 or print "cannot delete $oldlink.id\n";
+    unlink("$oldlink-src.id");
 }