Provide PDO_SOURCE_ROOT default for docker to allow zero-config build

Co-authored-by: Bruno Vavala <[email protected]>
Signed-off-by: g2flyer <[email protected]>

docker/Makefile

@@ -14,6 +14,14 @@
 # limitations under the License.
 # ------------------------------------------------------------------------------
 
+# PDO_SOURCE_ROOT
+# The directory to pick up PDO source when building containers.
+# Usually, below default should do the "right thing" but if your path
+# contains spaces or you want source from another directory than the parent,
+# you will have to explicitly pass, e.g. via make.loc (see below),
+# the desired PDO_SOURCE_ROOT when invoking make.
+PDO_SOURCE_ROOT ?= $(realpath $(dir $(abspath $(lastword $(MAKEFILE_LIST))))/../)
+
 # PDO_REPO --
 #   The URL or path to the git repository, the default uses the current repository
 #   though it might be reasonable to build a particular branch from the primary
@@ -37,11 +45,7 @@ PDO_GROUP_UID ?= $(shell id -g)
 # Include local customizations if they are available
 -include make.loc
 
-# Turns out that setting the script directory from the Makefile's name
-# does not work very well if the path contains spaces in the name; in
-# fact lots of things break very badly; set this explicitly
-DOCKER_DIR ?= ${PDO_SOURCE_ROOT}/docker
-
+DOCKER_DIR = ${PDO_SOURCE_ROOT}/docker
 DOCKER_USERNAME = $(LOGNAME)
 DOCKER_BUILDARGS += --build-arg UID=$(PDO_USER_UID)
 DOCKER_BUILDARGS += --build-arg GID=$(PDO_GROUP_UID)