i18n: make GETTEXT_POISON a runtime option

Change the GETTEXT_POISON compile-time + runtime GIT_GETTEXT_POISON
test parameter to only be a GIT_TEST_GETTEXT_POISON=<non-empty?>
runtime parameter, to be consistent with other parameters documented
in "Running tests with special setups" in t/README.

When I added GETTEXT_POISON in bb946bba76 ("i18n: add GETTEXT_POISON
to simulate unfriendly translator", 2011-02-22) I was concerned with
ensuring that the _() function would get constant folded if NO_GETTEXT
was defined, and likewise that GETTEXT_POISON would be compiled out
unless it was defined.

But as the benchmark in my [1] shows doing a one-off runtime
getenv("GIT_TEST_[...]") is trivial, and since GETTEXT_POISON was
originally added the GIT_TEST_* env variables have become the common
idiom for turning on special test setups.

So change GETTEXT_POISON to work the same way. Now the
GETTEXT_POISON=YesPlease compile-time option is gone, and running the
tests with GIT_TEST_GETTEXT_POISON=[YesPlease|] can be toggled on/off
without recompiling.

This allows for conditionally amending tests to test with/without
poison, similar to what 859fdc0c3c ("commit-graph: define
GIT_TEST_COMMIT_GRAPH", 2018-08-29) did for GIT_TEST_COMMIT_GRAPH. Do
some of that, now we e.g. always run the t0205-gettext-poison.sh test.

I did enough there to remove the GETTEXT_POISON prerequisite, but its
inverse C_LOCALE_OUTPUT is still around, and surely some tests using
it can be converted to e.g. always set GIT_TEST_GETTEXT_POISON=.

Notes on the implementation:

 * We still compile a dedicated GETTEXT_POISON build in Travis
   CI. Perhaps this should be revisited and integrated into the
   "linux-gcc" build, see ae59a4e44f ("travis: run tests with
   GIT_TEST_SPLIT_INDEX", 2018-01-07) for prior art in that area. Then
   again maybe not, see [2].

 * We now skip a test in t0000-basic.sh under
   GIT_TEST_GETTEXT_POISON=YesPlease that wasn't skipped before. This
   test relies on C locale output, but due to an edge case in how the
   previous implementation of GETTEXT_POISON worked (reading it from
   GIT-BUILD-OPTIONS) wasn't enabling poison correctly. Now it does,
   and needs to be skipped.

 * The getenv() function is not reentrant, so out of paranoia about
   code of the form:

       printf(_("%s"), getenv("some-env"));

   call use_gettext_poison() in our early setup in git_setup_gettext()
   so we populate the "poison_requested" variable in a codepath that's
   won't suffer from that race condition.

 * We error out in the Makefile if you're still saying
   GETTEXT_POISON=YesPlease to prompt users to change their
   invocation.

 * We should not print out poisoned messages during the test
   initialization itself to keep it more readable, so the test library
   hides the variable if set in $GIT_TEST_GETTEXT_POISON_ORIG during
   setup. See [3].

See also [4] for more on the motivation behind this patch, and the
history of the GETTEXT_POISON facility.

1. https://public-inbox.org/git/871s8gd32p.fsf@evledraar.gmail.com/
2. https://public-inbox.org/git/20181102163725.GY30222@szeder.dev/
3. https://public-inbox.org/git/20181022202241.18629-2-szeder.dev@gmail.com/
4. https://public-inbox.org/git/878t2pd6yu.fsf@evledraar.gmail.com/

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

1 files changed, 3 insertions, 3 deletions

diff --git a/t/t7201-co.sh b/t/t7201-co.sh
index 826987c..72b9b37 100755
--- a/t/t7201-co.sh
+++ b/t/t7201-co.sh
@@ -254,9 +254,9 @@ test_expect_success 'checkout to detach HEAD (with advice declined)' '
 test_expect_success 'checkout to detach HEAD' '
 	git config advice.detachedHead true &&
 	git checkout -f renamer && git clean -f &&
-	git checkout renamer^ 2>messages &&
-	test_i18ngrep "HEAD is now at 7329388" messages &&
-	(test_line_count -gt 1 messages || test -n "$GETTEXT_POISON") &&
+	GIT_TEST_GETTEXT_POISON= git checkout renamer^ 2>messages &&
+	grep "HEAD is now at 7329388" messages &&
+	test_line_count -gt 1 messages &&
 	H=$(git rev-parse --verify HEAD) &&
 	M=$(git show-ref -s --verify refs/heads/master) &&
 	test "z$H" = "z$M" &&