t: introduce PERL_TEST_HELPERS prerequisite

In the early days of Git, Perl was used quite prominently throughout the
project. This has changed significantly as almost all of the executables
we ship nowadays have eventually been rewritten in C. Only a handful of
subsystems remain that require Perl:

  - gitweb, a read-only web interface.

  - A couple of scripts that allow importing repositories from GNU Arch,
    CVS and Subversion.

  - git-send-email(1), which can be used to send mails.

  - git-request-pull(1), which is used to request somebody to pull from
    a URL by sending an email.

  - git-filter-branch(1), which uses Perl with the `--state-branch`
    option. This command is typically recommended against nowadays in
    favor of git-filter-repo(1).

  - Our Perl bindings for Git.

  - The netrc Git credential helper.

None of these subsystems can really be considered to be part of the
"core" of Git, and an installation without them is fully functional.
It is more likely than not that an end user wouldn't even notice that
any features are missing if those tools weren't installed. But while
Perl nowadays very much is an optional dependency of Git, there is a
significant limitation when Perl isn't available: developers cannot run
our test suite.

Preceding commits have started to lift this restriction by removing the
strict dependency on Perl in many central parts of the test library. But
there are still many tests that rely on small Perl helpers to do various
different things.

Introduce a new PERL_TEST_HELPERS prerequisite that guards all tests
that require Perl. This prerequisite is explicitly different than the
preexisting PERL prerequisite:

  - PERL records whether or not features depending on the Perl
    interpreter are built.

  - PERL_TEST_HELPERS records whether or not a Perl interpreter is
    available for our tests.

By having these two separate prerequisites we can thus distinguish
between tests that inherently depend on Perl because the underlying
feature does, and those tests that depend on Perl because the test
itself is using Perl.

Adapt all tests to set the PERL_TEST_HELPERS prerequisite as needed.

Signed-off-by: Patrick Steinhardt <[email protected]>
Signed-off-by: Junio C Hamano <[email protected]>

Author: pks-t

t/t0008-ignores.sh

@@ -5,6 +5,12 @@ test_description=check-ignore
 TEST_CREATE_REPO_NO_TEMPLATE=1
 . ./test-lib.sh
 
+if ! test_have_prereq PERL_TEST_HELPERS
+then
+	skip_all='skipping ignores tests; Perl not available'
+	test_done
+fi
+
 init_vars () {
 	global_excludes="global-excludes"
 }

t/t0021-conversion.sh

@@ -619,7 +619,7 @@ test_expect_success 'required process filter should be used only for "clean" ope
 	)
 '
 
-test_expect_success 'required process filter should process multiple packets' '
+test_expect_success PERL_TEST_HELPERS 'required process filter should process multiple packets' '
 	test_config_global filter.protocol.process "test-tool rot13-filter --log=debug.log clean smudge" &&
 	test_config_global filter.protocol.required true &&
 
@@ -684,7 +684,7 @@ test_expect_success 'required process filter should process multiple packets' '
 	)
 '
 
-test_expect_success 'required process filter with clean error should fail' '
+test_expect_success PERL_TEST_HELPERS 'required process filter with clean error should fail' '
 	test_config_global filter.protocol.process "test-tool rot13-filter --log=debug.log clean smudge" &&
 	test_config_global filter.protocol.required true &&
 	rm -rf repo &&

t/t0210-trace2-normal.sh

@@ -4,6 +4,12 @@ test_description='test trace2 facility (normal target)'
 
 . ./test-lib.sh
 
+if ! test_have_prereq PERL_TEST_HELPERS
+then
+	skip_all='skipping trace2 tests; Perl not available'
+	test_done
+fi
+
 # Turn off any inherited trace2 settings for this test.
 sane_unset GIT_TRACE2 GIT_TRACE2_PERF GIT_TRACE2_EVENT
 sane_unset GIT_TRACE2_BRIEF

t/t0211-trace2-perf.sh

@@ -4,6 +4,12 @@ test_description='test trace2 facility (perf target)'
 
 . ./test-lib.sh
 
+if ! test_have_prereq PERL_TEST_HELPERS
+then
+	skip_all='skipping trace2 tests; Perl not available'
+	test_done
+fi
+
 # Turn off any inherited trace2 settings for this test.
 sane_unset GIT_TRACE2 GIT_TRACE2_PERF GIT_TRACE2_EVENT
 sane_unset GIT_TRACE2_PERF_BRIEF

t/t0610-reftable-basics.sh

@@ -643,7 +643,7 @@ test_expect_success 'basic: commit and list refs' '
 	test_cmp actual expect
 '
 
-test_expect_success 'basic: can write large commit message' '
+test_expect_success PERL_TEST_HELPERS 'basic: can write large commit message' '
 	test_when_finished "rm -rf repo" &&
 	git init repo &&
 	perl -e "

t/t0613-reftable-write-options.sh

@@ -139,7 +139,7 @@ test_expect_success 'small block size leads to multiple ref blocks' '
 	)
 '
 
-test_expect_success 'small block size fails with large reflog message' '
+test_expect_success PERL_TEST_HELPERS 'small block size fails with large reflog message' '
 	test_when_finished "rm -rf repo" &&
 	git init repo &&
 	(

t/t1006-cat-file.sh

@@ -1270,7 +1270,7 @@ extract_batch_output () {
     ' "$@"
 }
 
-test_expect_success 'cat-file --batch-all-objects --batch ignores replace' '
+test_expect_success PERL_TEST_HELPERS 'cat-file --batch-all-objects --batch ignores replace' '
 	git cat-file --batch-all-objects --batch >actual.raw &&
 	extract_batch_output $orig <actual.raw >actual &&
 	{

t/t1007-hash-object.sh

@@ -205,23 +205,23 @@ test_expect_success 'too-short tree' '
 	grep "too-short tree object" err
 '
 
-test_expect_success 'malformed mode in tree' '
+test_expect_success PERL_TEST_HELPERS 'malformed mode in tree' '
 	hex_oid=$(echo foo | git hash-object --stdin -w) &&
 	bin_oid=$(echo $hex_oid | hex2oct) &&
 	printf "9100644 \0$bin_oid" >tree-with-malformed-mode &&
 	test_must_fail git hash-object -t tree tree-with-malformed-mode 2>err &&
 	grep "malformed mode in tree entry" err
 '
 
-test_expect_success 'empty filename in tree' '
+test_expect_success PERL_TEST_HELPERS 'empty filename in tree' '
 	hex_oid=$(echo foo | git hash-object --stdin -w) &&
 	bin_oid=$(echo $hex_oid | hex2oct) &&
 	printf "100644 \0$bin_oid" >tree-with-empty-filename &&
 	test_must_fail git hash-object -t tree tree-with-empty-filename 2>err &&
 	grep "empty filename in tree entry" err
 '
 
-test_expect_success 'duplicate filename in tree' '
+test_expect_success PERL_TEST_HELPERS 'duplicate filename in tree' '
 	hex_oid=$(echo foo | git hash-object --stdin -w) &&
 	bin_oid=$(echo $hex_oid | hex2oct) &&
 	{

t/t1010-mktree.sh

@@ -41,13 +41,13 @@ test_expect_success 'ls-tree piped to mktree (2)' '
 	test_cmp tree.withsub actual
 '
 
-test_expect_success 'ls-tree output in wrong order given to mktree (1)' '
+test_expect_success PERL_TEST_HELPERS 'ls-tree output in wrong order given to mktree (1)' '
 	perl -e "print reverse <>" <top |
 	git mktree >actual &&
 	test_cmp tree actual
 '
 
-test_expect_success 'ls-tree output in wrong order given to mktree (2)' '
+test_expect_success PERL_TEST_HELPERS 'ls-tree output in wrong order given to mktree (2)' '
 	perl -e "print reverse <>" <top.withsub |
 	git mktree >actual &&
 	test_cmp tree.withsub actual

t/t1450-fsck.sh

@@ -346,7 +346,7 @@ test_expect_success 'unparseable tree object' '
 	test_grep ! "fatal: empty filename in tree entry" out
 '
 
-test_expect_success 'tree entry with type mismatch' '
+test_expect_success PERL_TEST_HELPERS 'tree entry with type mismatch' '
 	test_when_finished "remove_object \$blob" &&
 	test_when_finished "remove_object \$tree" &&
 	test_when_finished "remove_object \$commit" &&
@@ -364,7 +364,7 @@ test_expect_success 'tree entry with type mismatch' '
 	test_grep ! "dangling blob" out
 '
 
-test_expect_success 'tree entry with bogus mode' '
+test_expect_success PERL_TEST_HELPERS 'tree entry with bogus mode' '
 	test_when_finished "remove_object \$blob" &&
 	test_when_finished "remove_object \$tree" &&
 	blob=$(echo blob | git hash-object -w --stdin) &&
@@ -984,7 +984,7 @@ corrupt_index_checksum () {
 
 # Corrupt the checksum on the index and then
 # verify that only fsck notices.
-test_expect_success 'detect corrupt index file in fsck' '
+test_expect_success PERL_TEST_HELPERS 'detect corrupt index file in fsck' '
 	cp .git/index .git/index.backup &&
 	test_when_finished "mv .git/index.backup .git/index" &&
 	corrupt_index_checksum &&