* Added a script nix-activate which builds a list of "activated"

  packages (i.e., the packages that should appear in the user's $PATH,
  and so on).  Based on this list, the script nix-populate creates a
  hierarchy of symlinks to the relevant files in those packages (e.g.,
  for pkg/bin and pkg/lib).  

  A nice property of nix-populate is that on each run it creates a
  *new* tree, rather than updating the old one.  It then atomically
  switches over to the new tree.  This allows atomic upgrades or
  rollbacks on the set of activated packages.

1 files changed, 22 insertions, 0 deletions

diff --git a/src/nix-activate b/src/nix-activate
new file mode 100755
index 000000000000..9fe6466866df
--- /dev/null
+++ b/src/nix-activate
@@ -0,0 +1,22 @@
+#! /usr/bin/perl -w
+
+use strict;
+
+my $pkglist = "/home/eelco/.nixactivations";
+
+if (!-f $pkglist) {
+    system "touch $pkglist";
+}
+
+my $hash;
+foreach $hash (@ARGV) {
+    system "grep -q $hash $pkglist";
+    if ($?) {
+	print STDERR "activating $hash\n";
+	system "nix getpkg $hash > /dev/null";
+	if ($?) { die "`nix getpkg' failed"; }
+	system "echo $hash >> $pkglist";
+    }
+}
+
+system "nix-populate";