tests: make GIT_TEST_GETTEXT_POISON a boolean

Change the GIT_TEST_GETTEXT_POISON variable from being "non-empty?" to
being a more standard boolean variable.

Since it needed to be checked in both C code and shellscript (via test
-n) it was one of the remaining shellscript-like variables. Now that
we have "env--helper" we can change that.

There's a couple of tricky edge cases that arise because we're using
git_env_bool() early, and the config-reading "env--helper".

If GIT_TEST_GETTEXT_POISON is set to an invalid value die_bad_number()
will die, but to do so it would usually call gettext(). Let's detect
the special case of GIT_TEST_GETTEXT_POISON and always emit that
message in the C locale, lest we infinitely loop.

As seen in the updated tests in t0017-env-helper.sh there's also a
caveat related to "env--helper" needing to read the config for trace2
purposes.

Since the C_LOCALE_OUTPUT prerequisite is lazy and relies on
"env--helper" we could get invalid results if we failed to read the
config (e.g. because we'd loop on includes) when combined with
e.g. "test_i18ngrep" wanting to check with "env--helper" if
GIT_TEST_GETTEXT_POISON was true or not.

I'm crossing my fingers and hoping that a test similar to the one I
removed in the earlier "config tests: simplify include cycle test"
change in this series won't happen again, and testing for this
explicitly in "env--helper"'s own tests.

This change breaks existing uses of
e.g. GIT_TEST_GETTEXT_POISON=YesPlease, which we've documented in
po/README and other places. As noted in [1] we might want to consider
also accepting "YesPlease" in "env--helper" as a special-case.

But as the lack of uproar over 6cdccfce1e ("i18n: make GETTEXT_POISON
a runtime option", 2018-11-08) demonstrates the audience for this
option is a really narrow set of git developers, who shouldn't have
much trouble modifying their test scripts, so I think it's better to
deal with that minor headache now and make all the relevant GIT_TEST_*
variables boolean in the same way than carry the "YesPlease"
special-case forward.

1. https://public-inbox.org/git/xmqqtvckm3h8.fsf@gitster-ct.c.googlers.com/

Signed-off-by: Ævar Arnfjörð Bjarmason <avarab@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

1 files changed, 2 insertions, 2 deletions

diff --git a/t/README b/t/README
index 9747971..9a131f4 100644
--- a/t/README
+++ b/t/README
@@ -343,8 +343,8 @@ whether this mode is active, and e.g. skip some tests that are hard to
 refactor to deal with it. The "SYMLINKS" prerequisite is currently
 excluded as so much relies on it, but this might change in the future.
 
-GIT_TEST_GETTEXT_POISON=<non-empty?> turns all strings marked for
-translation into gibberish if non-empty (think "test -n"). Used for
+GIT_TEST_GETTEXT_POISON=<boolean> turns all strings marked for
+translation into gibberish if true. Used for
 spotting those tests that need to be marked with a C_LOCALE_OUTPUT
 prerequisite when adding more strings for translation. See "Testing
 marked strings" in po/README for details.