test-lib: simplify by removing test_external

Remove the "test_external" function added in [1]. This arguably makes
the output of t9700-perl-git.sh and friends worse. But as we'll argue
below the trade-off is worth it, since "chaining" to another TAP
emitter in test-lib.sh is more trouble than it's worth.

The new output of t9700-perl-git.sh is now:

	$ ./t9700-perl-git.sh
	ok 1 - set up test repository
	ok 2 - use t9700/test.pl to test Git.pm
	# passed all 2 test(s)
	1..2

Whereas before this change it would be:

	$ ./t9700-perl-git.sh
	ok 1 - set up test repository
	# run 1: Perl API (perl /home/avar/g/git/t/t9700/test.pl)
	ok 2 - use Git;
	[... omitting tests 3..46 from t/t9700/test.pl ...]
	ok 47 - unquote escape sequences
	1..47
	# test_external test Perl API was ok
	# test_external_without_stderr test no stderr: Perl API was ok

At the time of its addition supporting "test_external" was easy, but
when test-lib.sh itself started to emit TAP in [2] we needed to make
everything surrounding the emission of the plan consider
"test_external". I added that support in [2] so that we could run:

	prove ./t9700-perl-git.sh :: -v

But since then in [3] the door has been closed on combining
$HARNESS_ACTIVE and -v, we'll now just die:

	$ prove ./t9700-perl-git.sh :: -v
	Bailout called.  Further testing stopped:  verbose mode forbidden under TAP harness; try --verbose-log
	FAILED--Further testing stopped: verbose mode forbidden under TAP harness; try --verbose-log

So the only use of this has been that *if* we had failure in one of
these tests we could e.g. in CI see which test failed based on the
test number. Now we'll need to look at the full verbose logs to get
that same information.

I think this trade-off is acceptable given the reduction in
complexity, and it brings these tests in line with other similar
tests, e.g. the reftable tests added in [4] will be condensed down to
just one test, which invokes the C helper:

	$ ./t0032-reftable-unittest.sh
	ok 1 - unittests
	# passed all 1 test(s)
	1..1

It would still be nice to have that ":: -v" form work again, it
never *really* worked, but even though we've had edge cases test
output screwing up the TAP it mostly worked between d998bd4ab67 and
[3], so we may have been overzealous in forbidding it outright.

I have local patches which I'm planning to submit sooner than later
that get us to that goal, and in a way that isn't buggy. In the
meantime getting rid of this special case makes hacking on this area
of test-lib.sh easier, as we'll do in subsequent commits.

The switch from "perl" to "$PERL_PATH" here is because "perl" is
defined as a shell function in the test suite, see a5bf824f3b4 (t:
prevent '-x' tracing from interfering with test helpers' stderr,
2018-02-25). On e.g. the OSX CI the "command perl"... will be part of
the emitted stderr.

1. fb32c410087 (t/test-lib.sh: add test_external and
   test_external_without_stderr, 2008-06-19)
2. d998bd4ab67 (test-lib: Make the test_external_* functions
   TAP-aware, 2010-06-24)
3. 614fe015212 (test-lib: bail out when "-v" used under
   "prove", 2016-10-22)
4. ef8a6c62687 (reftable: utility functions, 2021-10-07)

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

1 files changed, 0 insertions, 26 deletions

diff --git a/t/README b/t/README
index 0664aee7ed..98f69ed13d 100644
--- a/t/README
+++ b/t/README
@@ -938,32 +938,6 @@ see test-lib-functions.sh for the full list and their options.
 	    test_done
 	fi
 
- - test_external [<prereq>] <message> <external> <script>
-
-   Execute a <script> with an <external> interpreter (like perl). This
-   was added for tests like t9700-perl-git.sh which do most of their
-   work in an external test script.
-
-	test_external \
-	    'GitwebCache::*FileCache*' \
-	    perl "$TEST_DIRECTORY"/t9503/test_cache_interface.pl
-
-   If the test is outputting its own TAP you should set the
-   test_external_has_tap variable somewhere before calling the first
-   test_external* function. See t9700-perl-git.sh for an example.
-
-	# The external test will outputs its own plan
-	test_external_has_tap=1
-
- - test_external_without_stderr [<prereq>] <message> <external> <script>
-
-   Like test_external but fail if there's any output on stderr,
-   instead of checking the exit code.
-
-	test_external_without_stderr \
-	    'Perl API' \
-	    perl "$TEST_DIRECTORY"/t9700/test.pl
-
  - test_expect_code <exit-code> <command>
 
    Run a command and ensure that it exits with the given exit code.