pull nixos-mailserver module into this repo

nixos-mailserver/sieve-report-spam-ham.nix

@@ -0,0 +1,30 @@
+{ stdenv, dovecot_pigeonhole}:
+
+stdenv.mkDerivation rec {
+  name = "sieve-report-spam-ham";
+
+  src = ./sieve-report-spam-ham;
+
+  phases = [ "copyPhase" "compilePhase" ];
+
+  copyPhase = ''
+    mkdir $out
+    cp -Rv $src/. $out/
+    find $out -type d -exec chmod -c 0755 {} \;
+    set +x
+    '';
+
+  # Yeah, need a specific dovecot.conf to enable the necessary plugins...
+  # taking the one used by the dovecot that actually executes the sieve scripts should
+  # work as well, but passing it through isn't worth my time.
+  compilePhase = ''
+    dc=$(pwd)/dovecot.conf
+    cat > $dc <<-EOF
+      plugin {
+        sieve_plugins = sieve_imapsieve sieve_extprograms
+        sieve_global_extensions = +vnd.dovecot.pipe +vnd.dovecot.environment
+      }
+    EOF
+    find $out -iname '*.sieve' -print0 | xargs -t -0 -n1 ${dovecot_pigeonhole}/bin/sievec -c $dc
+  '';
+}