fixup! Some minor docker improvements

Signed-off-by: g2flyer <[email protected]>

docker/Makefile

@@ -25,7 +25,14 @@
 PDO_REPO ?= ${PDO_SOURCE_ROOT}
 PDO_BRANCH ?= $(shell git rev-parse --abbrev-ref HEAD)
 
-PDO_VERSION ?= $(shell cd repository; bin/get_version) 
+# PDO_VERSION, the version tag which we derive from latest version among git version tags
+#    and commit-length derived patch version part.
+#    Note 
+#    - to deal with empty and/or updated repository directory we give it
+#      latest as default and define it as a lazily evaluated shell variable
+#    - this also implies this variable can used only in (shell) actions and not in defining
+#      other Make variables, dependencies or alike!
+PDO_VERSION ?= $$( if [ -d $(PDO_REPO)/docker/repository ]; then cd $(PDO_REPO)/docker/repository; bin/get_version ; else echo "latest"; fi)
 
 # PDO_USER_UID, PDO_GROUP_UID --
 #   The UID/GID for the user accounts that will be created in the container; this is