lib/str.sh gains firstword, lastword, or, patsubst, filter, filter_out,
addprefix, addsuffix and jwt: what the catalogue .mk files are written in.
The make JWT macro split on the commas of its payload; this one does not.
lib/context.sh registers COMPOSE_PROJECT_NAME, APP, DOCKER_NETWORK_* and the
rest as lazy defaults, so a converted .mk keeps reading them as it did.
Hooks also load a directory-level _stack.env and _stack.sh, for the .mk files
of the catalogue that hold settings for several stacks at once.
Ported from make/utils.mk, make/def.mk, make/apps/def.docker.mk and
make/apps/def.mk, with the examples that sat as dead comments in
make/apps/def.mk turned into actual assertions.
Two deviations from the make macros are pinned and documented in DELTAS.md;
both only show up on code paths nothing uses.
Yann Autissier