Add the script from common-bump-milestone.

It's a good script that does good things. Having it in VC seems friendly.

Change-Id: I221101f3012a4df416635399d24a0a2f6d9bcd99

modules/jenkins_slave/files/slave_scripts/bump-milestone.sh

@@ -0,0 +1,56 @@
+#!/bin/bash -xe
+
+# This script store release meta information in the git repository for
+# a project.  It does so on an isolated, hidden branch called
+# refs/meta/openstack/release.  Because it's not under refs/heads, a
+# standard clone won't retrieve it or cause it to show up in the list
+# of remote branches.  The branch shares no history witht the project
+# itself; it starts with its own root commit.  Jenkins is permitted to
+# push directly to refs/meta/openstack/*.
+
+GIT_HOST="review.openstack.org:29418"
+PROJECT_PREFIX="openstack"
+
+if [[ ! -e ${PROJECT} ]]; then
+  git clone ssh://$GIT_HOST/$PROJECT_PREFIX/$PROJECT
+fi
+cd $PROJECT
+git checkout master
+
+# Get the list of meta refs
+git fetch origin +refs/meta/*:refs/remotes/meta/*
+
+# Checkout or create the meta/openstack/release branch
+if ! { git branch -a |grep ^[[:space:]]*remotes/meta/openstack/release$; }
+then
+  git checkout --orphan release
+  # Delete everything so the first commit is truly empty:
+  git rm -rf .
+  # git rm -rf leaves submodule directories:
+  find -maxdepth 1 -not -regex '\./\.git\(/.*\)?' -not -name . -exec rm -fr {} \;
+  ls -la
+else
+  git branch -D release || /bin/true
+  git checkout -b release remotes/meta/openstack/release
+fi
+
+# Normally a branch name will just be a file, but we can have branches
+# like stable/diablo, so in that case, make the "stable/" directory
+# if needed:
+mkdir -p `dirname $BRANCH`
+
+# Read and update the value for the branch
+if [ -e "$BRANCH" ]
+then
+  echo "Current contents of ${BRANCH}:"
+  cat "${BRANCH}"
+else
+  echo "${BRANCH} does not exist. Creating it."
+fi
+
+echo "Updating ${BRANCH} to read $VALUE"
+echo "$VALUE" > ${BRANCH}
+git add ${BRANCH}
+
+git commit -m "Milestone ${BRANCH} set to $VALUE"
+git push origin HEAD:refs/meta/openstack/release