Re: [PATCH] test-lib.sh: use GIT_TEST_COLUMNS over COLUMNS

On Tue, Jul 27, 2021 at 01:57:09AM +0200, Ævar Arnfjörð Bjarmason wrote:

In my c49a177beca (test-lib.sh: set COLUMNS=80 for --verbose
repeatability, 2021-06-29) the test suite started breaking on recent
versions of bash.

This is because it sets "shopt -s checkwinsize" starting with version
5.0, furthermore it started setting COLUMNS under "shopt -s
checkwinsize" for non-interactive use around version 4.3.

A narrow fix for that issue would be to add this just above our
setting of COLUMNS in test-lib.sh:

	shopt -u checkwinsize >/dev/null 2>&1

But we'd then be at the mercy of the next shell or terminal that wants
to be clever about COLUMNS.

Let's instead solve this more thoroughly. We'll now take
GIT_TEST_COLUMNS over COLUMNS, and furthermore intentionally spoil the
COLUMNS variable to break any tests that rely on it being set to a
sane value.

If something breaks because we have a codepath that's not
term_columns() checking COLUMNS we'd like to know about it, the narrow
"shopt -u checkwinsize" fix won't give us that.

I guess people running with bash won't see the test breakage (because
bash will quietly "fix" the COLUMNS setting). But enough people run with
/bin/sh that we'll eventually notice.

This approach does mean that any tests of ours that expected to test
term_columns() behavior by setting COLUMNS will need to explicitly
unset GIT_TEST_COLUMNS, or set it to the empty string. I'm doing the
latter in all the tests changed here.

This is rather ugly, and I'm not in general a fan of adding more
test-only code into the bowels of Git itself. But it may be the least
bad solution.

The only alternative I could come up with is _not_ to set COLUMNS
everywhere, but instead insist on each individual test manually doing
"COLUMNS=80 git ...". Setting it as a one-shot seems to be reliable
enough. The downside is just that various tests will need to do so. We
already have quite a few that do, but I guess anything that uses the
progress meter is now subject to it.

-Peff