docker: unite Dockerfiles; auto-deploy images to DockerHub (#9329)

* Unite Dockerfiles - add build/run/push scripts
* update docker documentation
* update .travis.yml
* switch to using a preprocessor on Dockerfiles
* skip building docker images on pull requests
* update files with copyright info
* tweak when travis builds for docker files are done

share/spack/docker/entrypoint.bash

+#! /usr/bin/env bash -e
+#
+# Copyright 2013-2018 Lawrence Livermore National Security, LLC and other
+# Spack Project Developers. See the top-level COPYRIGHT file for details.
+#
+# SPDX-License-Identifier: (Apache-2.0 OR MIT)
+
+if [ "$1" '=' 'docker-shell' ] ; then
+    if [ -t 0 ] ; then
+        exec bash -il
+    else
+        (
+            echo -n "It looks like you're trying to run an intractive shell"
+            echo -n " session, but either no psuedo-TTY is allocateed for this"
+            echo -n " container's STDIN, or it is closed."
+            echo
+
+            echo -n "Make sure you run docker with the --interactive and --tty"
+            echo -n " options."
+            echo
+        ) >&2
+
+        exit 1
+    fi
+else
+    exec 3>&1
+    exec 4>&2
+
+    exec 1>&-
+    exec 2>&-
+
+    source /etc/profile.d/spack.sh
+    source /etc/profile.d/handle-ssh.sh
+
+    exec 1>&3
+    exec 2>&4
+
+    exec 3>&-
+    exec 4>&-
+
+    spack "$@"
+    exit $?
+fi

share/spack/docker/build/common/handle-prompt.sh → share/spack/docker/handle-prompt.sh

@@ -3,6 +3,8 @@
 #
 # SPDX-License-Identifier: (Apache-2.0 OR MIT)
 
+if [ x$SPACK_PROMPT '!=' x0 ] ; then
+
 __tmp="`mktemp -d`"
 
 __trylock() {
@@ -83,7 +85,7 @@ __git_head() {
 __update_prompt() {
     local prompt
     prompt=''
-    linux_distro="$DISTRO"
+    linux_distro="$DOCKERFILE_DISTRO"
     if [ -n "$linux_distro" ] ; then
         linux_distro='\[\e[1;34m\][\[\e[0;34m\]'"$linux_distro"'\[\e[1;34m\]]'
         if [ -n "$prompt" ] ; then
@@ -163,3 +165,5 @@ __update_prompt_main() {
 }
 
 PROMPT_COMMAND=__update_prompt_main
+
+fi # [ x$SPACK_PROMPT '!=' x0 ]

share/spack/docker/push-image.sh

+./build-image.sh
\ No newline at end of file

share/spack/docker/render-image-template.sh

+./build-image.sh
\ No newline at end of file

share/spack/docker/run-image.sh

+build-image.sh
\ No newline at end of file