add min-copy-closure, a minimal nix-copy-closure substitute

pkgs/default.nix

@@ -45,5 +45,6 @@
 
   openwrt = callPackage ./openwrt {};
 
+  min-copy-closure = callPackage ./min-copy-closure {};
   hi = callPackage ./hi {};
 }

pkgs/min-copy-closure/default.nix

@@ -0,0 +1,13 @@
+{
+  stdenv
+, nix
+, cpio
+}: stdenv.mkDerivation {
+  name = "min-copy-closure";
+  buildInputs = [ nix cpio ];
+  src = ./.;
+  installPhase = ''
+    mkdir -p $out/bin
+    cp min-copy-closure.sh $out/bin/nix-copy-closure
+  '';
+}

pkgs/min-copy-closure/min-copy-closure.fnl

@@ -0,0 +1,2 @@
+
+(local ssh (io.popen "

pkgs/min-copy-closure/min-copy-closure.sh

@@ -0,0 +1,40 @@
+#!/usr/bin/env bash
+
+target_host=$1
+shift
+
+paths=$(nix-store -q --requisites "$@")
+needed=""
+
+coproc remote {
+    ssh -C ${target_host}
+}
+
+exec 10>&${remote[1]}
+
+for p in $paths; do
+    echo "test -e $p && echo skip || echo $p"  >&10
+    read n <&${remote[0]}
+    case $n in
+	skip)
+	    :
+	    ;;
+	*)
+	    needed="${needed} $n"
+	    echo Will copy $n
+	    ;;
+    esac
+done
+
+if test -z "$needed" ; then
+    echo Nothing to copy
+    exit 1
+fi
+
+echo "cd / && cpio -v -i >/dev/console"  >&10
+
+find $needed | cpio -H newc -o  >&10
+
+echo "date"  >&10
+read n <&${remote[0]}
+echo $n

pkgs/min-copy-closure/receive.sh

@@ -0,0 +1,9 @@
+#!/usr/bin/env sh
+cd /nix/store
+while read f ; do
+    test "$f" = "end" && break
+    test -e $f || echo -n $f " "
+done
+mkdir -p /tmp/store
+cd /tmp/store
+cpio -i