Two mechanisms, matching what the make engine actually did:
Lazy defaults. A stack setting is a function myos_default_<VAR>, called only
when the variable has no value, and called again at every reference. That is
exactly a recursive ?=: an explicit value wins, and the default follows a
DOMAIN that a .env changes later. The prefix is what makes it safe; the first
version used a bare function named after the variable, and the test suite
caught it running /usr/bin/host for a stack group called host.
Templates. myos env-update fills a .env from the .env.dist files, expanding
${VAR} against the current values and running $(command), forward references
included.
Also fixed: the project .env now wins over /etc/conf.d/myos, which is what the
documentation claimed and the code did not.
share/make/shim.mk lets a project keep make as a front end: every myos command
becomes a target that shells out to bin/myos, and the project keeps its own
targets and its stack .mk files. It sits outside make/ because the legacy
engine globs every .mk in there.
An install under a custom prefix (--prefix ~/.local) could not find the
catalogue it had just cloned into <prefix>/share/myos: only the three system
paths were searched.
A stack is a directory of compose files; the current directory is a stack when
it holds one. The same command works for a project, a catalogue stack, a group
and a host singleton, and stacks sharing a project are now a single compose
call.
Two traps of the make engine are closed on the way: an unknown command is an
error instead of a silent success, and a group is only expanded when its name
is lowercase, so an environment variable can no longer be mistaken for one.
That guard spells out its character class because a-z matches uppercase too
under a dictionary collation.
Replaces the 500-character stack_path expression of
make/apps/def.docker.mk:159 and its leaked $(stackz) loop variable with
three readable functions, covered by 20 assertions.
Yann Autissier