dockerTools: remove tarballs functionality

I think the intention of this functionality was to provide a simple
alternative to the "runAsRoot" and "contents" attributes.

The implementation caused very slow builds of Docker images. Almost all
of the build time was spent in IO for tar, due to tarballs being
created, immediately extracted, then recreated. I had 30 minute builds
on some of my images which are now down to less than 2 minutes. A couple
of other users on #nix IRC have observed similar improvements.

The implementation also mutated the produced Docker layers without
changing their hashes. Using non-empty tarballs would produce images
which got cached incorrectly in Docker.

I have a commit which just fixes the performance problem but I opted to
completely remove the tarball feature after I found out that it didn't
correctly implement the Docker Image Specification due to the broken
hashing.

pkgs/build-support/docker/default.nix

@@ -45,27 +45,6 @@ rec {
       done
     '';
   
-  mkTarball = { name ? "docker-tar", drv, onlyDeps ? false }:
-    runCommand "${name}.tar.gz" rec {
-      inherit drv onlyDeps;
-      
-      drvClosure = writeReferencesToFile drv;
-      
-    } ''
-      while read dep; do
-        echo Copying $dep
-        dir="$(dirname "$dep")"
-        mkdir -p "rootfs/$dir"
-        cp -drf --preserve=mode $dep "rootfs/$dir/"
-      done < "$drvClosure"
-
-      if [ -z "$onlyDeps" ]; then
-        cp -drf --preserve=mode $drv/* rootfs/
-      fi
-      
-      tar -C rootfs/ -cpzf $out .
-    '';
-
   shellScript = text:
     writeScript "script.sh" ''
       #!${stdenv.shell}
@@ -99,16 +78,6 @@ EOF
     fi
   '';
 
-  # Append to tar instead of unpacking
-  mergeTarballs = tarballs:
-    runCommand "merge-tars" { inherit tarballs; } ''
-      mkdir tmp
-      for tb in $tarballs; do
-        tar -C tmp -xkpf $tb
-      done
-      tar -C tmp -cpzf $out .
-    '';
-
   runWithOverlay = { name , fromImage ? null, fromImageName ? null, fromImageTag ? null
                    , diskSize ? 1024, preMount ? "", postMount ? "", postUmount ? "" }:
     vmTools.runInLinuxVM (
@@ -182,7 +151,7 @@ EOF
 
       postMount = ''
         echo Packing raw image
-        tar -C mnt -czf $out .
+        tar -C mnt -cf $out .
       '';
     };
     
@@ -262,8 +231,8 @@ EOF
   # 6. repack the image
   buildImage = args@{ name, tag ? "latest"
                , fromImage ? null, fromImageName ? null, fromImageTag ? null
-               , contents ? null, tarballs ? [], config ? null
-               , runAsRoot ? null, diskSize ? 1024, extraCommands ? "" }:
+               , contents ? null, config ? null, runAsRoot ? null
+               , diskSize ? 1024, extraCommands ? "" }:
 
     let
 
@@ -275,14 +244,10 @@ EOF
           os = "linux";
           config = config;
       });
-      
+
       layer = (if runAsRoot == null
                then mkPureLayer { inherit baseJson contents extraCommands; }
                else mkRootLayer { inherit baseJson fromImage fromImageName fromImageTag contents runAsRoot diskSize extraCommands; });
-      depsTarball = mkTarball { name = "${baseName}-deps";
-                                drv = layer;
-                                onlyDeps = true; };
-      
       result = runCommand "${baseName}.tar.gz" {
         buildInputs = [ jshon ];
 
@@ -290,7 +255,7 @@ EOF
         imageTag = tag;
         inherit fromImage baseJson;
 
-        mergedTarball = if tarballs == [] then depsTarball else mergeTarballs ([ depsTarball ] ++ tarballs);
+        layerClosure = writeReferencesToFile layer;
 
         passthru = {
           buildArgs = args;
@@ -320,22 +285,17 @@ EOF
         mkdir temp
         cp ${layer}/* temp/
         chmod ug+w temp/*
-        
-        echo Adding dependencies
+
+        touch layerFiles
+        for dep in $(cat $layerClosure); do
+          find $dep >> layerFiles
+        done
+
+        echo Adding layer
         tar -tf temp/layer.tar >> baseFiles
-        tar -tf "$mergedTarball" | grep -v ${layer} > layerFiles
-        if [ "$(wc -l layerFiles|cut -d ' ' -f 1)" -gt 3 ]; then
-          sed -i -e 's|^[\./]\+||' baseFiles layerFiles
-          comm <(sort -n baseFiles|uniq) <(sort -n layerFiles|uniq) -1 -3 > newFiles
-          mkdir deps
-          pushd deps
-          tar -xpf "$mergedTarball" --no-recursion --files-from ../newFiles 2>/dev/null || true
-          tar -rf ../temp/layer.tar --no-recursion --files-from ../newFiles 2>/dev/null || true
-          popd
-        else
-          echo No new deps, no diffing needed
-        fi 
-        
+        comm <(sort -n baseFiles|uniq) <(sort -n layerFiles|uniq|grep -v ${layer}) -1 -3 > newFiles
+        tar -rpf temp/layer.tar --no-recursion --files-from newFiles 2>/dev/null || true
+
         echo Adding meta
         
         if [ -n "$parentID" ]; then