Re: [PATCH] Makefile: add and use the ".DELETE_ON_ERROR" flag

Jeff King [off-list ref] writes:

Yeah, I can see the view that running the test suite as a basic sanity
check may have value, if it's backed by more careful testing later (and
certainly while I'm developing, I wouldn't hesitate to run a subset of
the test suite to see how my work is progressing).

My main point was that I don't see much reason to do work to make that
kind of continuous "make test" work with simultaneous recompiles and
test-runs, if we can encourage people to do it more robustly with a
single compile-and-test-run loop. Maybe adding in the extra workdir
there makes it too heavy-weight? (Certainly my "ci" script is overkill,
but it seems like a loop of "reset to the current branch tip, compile,
run" in a worktree would be the minimal thing).

I actually do use such a "runs tests in the background while I am
not watching", so I am sympathetic to the higher-level goal, but I
find any execution of the idea that requires "let's reduce the
window where freshly built 'git' or any other things are not ready
by forcing 'mv $@+ $@' trick for added atomicity" simply insane and
not worth supporting.

Tests are run to find cases where things go wrong, and it is a waste
of cycles if that background task is not being run in isolation and
on a stable state.  A separate working tree is so easy to set up
these days, I do not see a point in complicating the build procedure
to avoid using it.