diff -r 1335bbfb066f -r 1868db0d1515 contrib/packaging/dockerlib.sh
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/contrib/packaging/dockerlib.sh	Sat May 12 10:33:11 2018 -0700
@@ -0,0 +1,42 @@
+#!/bin/sh -eu
+
+# This function exists to set up the DOCKER variable and verify that
+# it's the binary we expect. It also verifies that the docker service
+# is running on the system and we can talk to it.
+function checkdocker() {
+  if which docker.io >> /dev/null 2>&1 ; then
+    DOCKER=docker.io
+  elif which docker >> /dev/null 2>&1 ; then
+    DOCKER=docker
+  else
+    echo "Error: docker must be installed"
+    exit 1
+  fi
+
+  $DOCKER -h 2> /dev/null | grep -q Jansens && { echo "Error: $DOCKER is the Docking System Tray - install docker.io instead"; exit 1; }
+  $DOCKER version | grep -Eq "^Client( version)?:" || { echo "Error: unexpected output from \"$DOCKER version\""; exit 1; }
+  $DOCKER version | grep -Eq "^Server( version)?:" || { echo "Error: could not get docker server version - check it is running and your permissions"; exit 1; }
+}
+
+# Construct a container and leave its name in $CONTAINER for future use.
+function initcontainer() {
+  [ "$1" ] || { echo "Error: platform name must be specified"; exit 1; }
+
+  DFILE="$ROOTDIR/contrib/packaging/docker/$1"
+  [ -f "$DFILE" ] || { echo "Error: docker file $DFILE not found"; exit 1; }
+
+  CONTAINER="hg-dockerrpm-$1"
+  DBUILDUSER=build
+  (
+    cat $DFILE
+    if [ $(uname) = "Darwin" ] ; then
+        # The builder is using boot2docker on OS X, so we're going to
+        # *guess* the uid of the user inside the VM that is actually
+        # running docker. This is *very likely* to fail at some point.
+        echo RUN useradd $DBUILDUSER -u 1000
+    else
+        echo RUN groupadd $DBUILDUSER -g `id -g` -o
+        echo RUN useradd $DBUILDUSER -u `id -u` -g $DBUILDUSER -o
+    fi
+  ) | $DOCKER build --build-arg http_proxy --build-arg https_proxy --tag $CONTAINER -
+}