default docker tag to git ref

if DOCKER_TAG is not set, set a tag corresponding to the git ref
e.g. if the branch is `wip/foo_bar`, the tag will be `wip-foo_bar`

if the DOCKER_TAG is set, it will still take precedence.

This new behavior ensures that builds from different branches
will not collide, and is a prerequisite for enabling automatic builds.

kolla-build.conf

@@ -4,7 +4,10 @@ maintainer = University of Chicago
 registry = ghcr.io
 namespace = chameleoncloud/kolla
 openstack_release = xena
-tag = xena
+
+# tag is set in run.sh, not here
+# tag = xena
+
 type = source
 base = ubuntu
 base_tag = "20.04"

run.sh

@@ -34,7 +34,18 @@ fi
 
 # Set these _after_ sourcing a possible .env file, so it can be defaulted there.
 KOLLA_BRANCH="${KOLLA_BRANCH:-chameleoncloud/xena}"
-DOCKER_TAG="${DOCKER_TAG:-xena}"
+
+# by default, tag containers with the git sha for kolla-containers repo
+GIT_REF="$(git rev-parse --abbrev-ref HEAD)"
+
+# replace '/' with '-' since container tags cannot contain '/'
+GIT_REF_DASH=${GIT_REF//'/'/"-"}
+if [[ -n $(git status --porcelain) ]]; then
+  GIT_REF_DASH="${GIT_REF_DASH}-dirty"
+fi
+
+# if DOCKER_TAG env var is set, use that, otherwise use git ref as tag
+export DOCKER_TAG="${DOCKER_TAG:-$GIT_REF_DASH}"
 
 # Automatically update dependencies
 if [[ "${CHECK_UPDATES}" == "yes" || "${FORCE_UPDATES}" == "yes" ]]; then