common.sh: add docker_images_require

Clone docker-playground.git, source its jenkins-common.sh and run
docker_images_require from there. This will make it possible to run
osmocom-release-tarballs.sh in a docker container, for which the
Dockerfile is stored in docker-playground.git.

Related: OS#3870
Change-Id: Ic4519ccb6978793054869862f8ca0e21d9cf5be4

.gitignore

@@ -9,6 +9,7 @@ __pycache__/
 _temp/
 _deps/
 _release_tarballs/
+_docker_playground
 
 # osmocom-nightly-packages.sh
 nightly-3g_*

scripts/common.sh

@@ -27,6 +27,8 @@ OSMO_RELEASE_REPOS="
 	osmocom-bb
 "
 
+OSMO_BRANCH_DOCKER_PLAYGROUND="${OSMO_BRANCH_DOCKER_PLAYGROUND:-master}"
+
 # Print commit of HEAD for an Osmocom git repository, e.g.:
 # "f90496f577e78944ce8db1aa5b900477c1e479b0"
 # $1: repository
@@ -96,3 +98,27 @@ osmo_source_subdir() {
 			;;
 	esac
 }
+
+# Build docker images from docker-playground.git.
+# $1...$n: docker image names (e.g. "debian-stretch-build")
+docker_images_require() {
+	local oldpwd="$PWD"
+
+	# Get docker-plaground.git
+	if [ -d "_docker_playground" ]; then
+		git -C _docker_playground fetch
+	else
+		git clone https://git.osmocom.org/docker-playground/ _docker_playground
+	fi
+	cd _docker_playground
+	git checkout "$OSMO_BRANCH_DOCKER_PLAYGROUND"
+	git reset --hard "origin/$OSMO_BRANCH_DOCKER_PLAYGROUND"
+
+	# jenkins-common.sh expects to run from a subdir in docker-playground.git
+	cd "$1"
+
+	# Subshell: run docker_images_require from jenkins-common.sh, pass all arguments
+	(. ../jenkins-common.sh; docker_images_require "$@")
+
+	cd "$oldpwd"
+}