Begin to split up overlay-local-store tests

The bad-uris tests are now in their own file.
"Outer" is a bad name, but it will be split up next.

tests/overlay-local-store/common.sh

@@ -0,0 +1,52 @@
+source ../common.sh
+
+requireEnvironment () {
+    requireSandboxSupport
+    [[ $busybox =~ busybox ]] || skipTest "no busybox"
+    if [[ $(uname) != Linux ]]; then skipTest "Need Linux for overlayfs"; fi
+    needLocalStore "The test uses --store always so we would just be bypassing the daemon"
+}
+
+setupConfig () {
+    echo "drop-supplementary-groups = false" >> "$NIX_CONF_DIR"/nix.conf
+    echo "build-users-group = " >> "$NIX_CONF_DIR"/nix.conf
+}
+
+storeDirs () {
+    storeA="$TEST_ROOT/store-a"
+    storeBTop="$TEST_ROOT/store-b"
+    storeB="local-overlay?root=$TEST_ROOT/merged-store&lower-store=$storeA&upper-layer=$storeBTop"
+    # Creating testing directories
+    mkdir -p "$TEST_ROOT"/{store-a/nix/store,store-b,merged-store/nix/store,workdir}
+}
+
+# Mounting Overlay Store
+mountOverlayfs () {
+  mount -t overlay overlay \
+    -o lowerdir="$storeA/nix/store" \
+    -o upperdir="$storeBTop" \
+    -o workdir="$TEST_ROOT/workdir" \
+    "$TEST_ROOT/merged-store/nix/store" \
+    || skipTest "overlayfs is not supported"
+
+  cleanupOverlay () {
+    umount "$TEST_ROOT/merged-store/nix/store"
+    rm -r $TEST_ROOT/workdir
+  }
+  trap cleanupOverlay EXIT
+}
+
+toRealPath () {
+  storeDir=$1; shift
+  storePath=$1; shift
+  echo $storeDir$(echo $storePath | sed "s^$NIX_STORE_DIR^^")
+}
+
+initLowerStore () {
+  # Init lower store with some stuff
+  nix-store --store "$storeA" --add ../dummy
+
+  # Build something in lower store
+  drvPath=$(nix-instantiate --store $storeA ../hermetic.nix --arg busybox "$busybox" --arg seed 1)
+  path=$(nix-store --store "$storeA" --realise $drvPath)
+}