Add pre-ci job generation for a multi-repo setup

.gitlab-ci.yml

+generate ci jobs:
+  script:
+    - "./bin/generate-gitlab-ci-yml.sh"
+  tags:
+    - "spack-k8s"
+  image: "spack/ubuntu:18.04"
+  artifacts:
+    paths:
+      - ci-generation
+    when: always

bin/generate-gitlab-ci-yml.sh

+#! /usr/bin/env bash
+
+# Remember where we are initially, it's the repo cloned by gitlab-ci
+original_directory=$(pwd)
+. "${original_directory}/share/spack/setup-env.sh"
+
+# Create a temporary working directory
+temp_dir=$(mktemp -d)
+trap 'rm -rf "$temp_dir"' INT TERM QUIT EXIT
+
+if [ -z "${DOWNSTREAM_CI_REPO}" ] ; then
+    echo "ERROR: missing variable: DOWNSTREAM_CI_REPO" >&2
+    exit 1
+fi
+
+if [ -z "${SPACK_RELEASE_ENVIRONMENT_PATH}" ] ; then
+    echo "ERROR: missing variable: SPACK_RELEASE_ENVIRONMENT_PATH" >&2
+    exit 1
+fi
+
+if [ -z "${CDASH_AUTH_TOKEN}" ] ; then
+    echo "ERROR: missing variable: CDASH_AUTH_TOKEN" >&2
+    exit 1
+fi
+
+if [ -z "${SPACK_RELEASE_ENVIRONMENT_REPO}" ] ; then
+    echo "Assuming spack repo contains environment" >&2
+    env_repo_dir=${original_directory}
+else
+    echo "Cloning ${SPACK_RELEASE_ENVIRONMENT_REPO} into ${temp_dir}/envrepo" >&2
+    cd ${temp_dir}
+    git clone ${SPACK_RELEASE_ENVIRONMENT_REPO} envrepo
+    cd envrepo
+    env_repo_dir=$(pwd)
+fi
+
+current_branch="$CI_COMMIT_REF_NAME"
+
+# Because want to see generated gitlab-ci file as an artifact,
+# we need to write it within the spack repo cloned by gitlab-ci.
+gen_ci_dir="${original_directory}/ci-generation"
+gen_ci_file="${gen_ci_dir}/.gitlab-ci.yml"
+mkdir -p ${gen_ci_dir}
+
+env_dir="${env_repo_dir}/${SPACK_RELEASE_ENVIRONMENT_PATH}"
+
+if [ ! -f "${env_dir}/spack.yaml" ] ; then
+    echo "ERROR: Cannot find spack environment file in ${env_dir}"
+    exit 1
+fi
+
+cd $env_dir
+
+token_file="${temp_dir}/cdash_auth_token"
+echo ${CDASH_AUTH_TOKEN} > ${token_file}
+
+# This commands generates the .gitlab-ci.yml and creates buildgroup in cdash
+spack release-jobs --force --output-file ${gen_ci_file} --cdash-credentials ${token_file}
+
+if [[ $? -ne 0 ]]; then
+    echo "spack release-jobs command failed"
+    exit 1
+fi
+
+cp ${gen_ci_file} "${original_directory}/.gitlab-ci.yml"
+
+git config --global user.email "robot@spack.io"
+git config --global user.name "Build Robot"
+
+commit_msg="Auto-generated commit testing ${current_branch} (${CI_COMMIT_SHA})"
+
+cd ${original_directory}
+echo "git status"
+git status
+echo "git branch"
+git branch -D ___multi_ci___ 2> /dev/null || true
+echo "git checkout"
+git checkout -b ___multi_ci___
+echo "git add"
+git add .gitlab-ci.yml
+echo "git commit"
+git commit -m "$commit_msg"
+echo "git commit-tree/reset"
+# Prepare to send the whole working copy.  Doing this instead should be faster
+# until we decide to come up with a way of automatically keeping the downstream
+# repo in sync with the main one, at which point just pushing a single, new
+# commit with the change would be faster.
+git reset "$( git commit-tree HEAD^{tree} -m ${commit_msg} )"
+echo "git status"
+git status
+echo "git push"
+git push --force "$DOWNSTREAM_CI_REPO" \
+    "___multi_ci___:multi-ci-${current_branch}"