t: introduce WITH_BREAKING_CHANGES prerequisite

Earlier c5bc9a7 (Makefile: wire up build option for deprecated
features, 2025-01-22) made an unfortunate decision to introduce the
WITHOUT_BREAKING_CHANGES prerequisite to perform tests that ensure
the historical behaviour that may be different from what we will
have in the future.  It would inevitably invite double-negation when
we need to add tests to ensure the behaviour we want to have in the
future.

Introduce WITH_BREAKING_CHANGES prerequisite and replace the
existing uses of WITHOUT_BREAKING_CHANGES prerequisite.  To catch
any future topics that add more uses of WITHOUT_BREAKING_CHANGES,
mark it as a removed prerequisite.

Signed-off-by: Junio C Hamano <gitster@pobox.com>

Author: gitster

t/t5323-pack-redundant.sh

@@ -36,7 +36,7 @@ relationship between packs and objects is as follows:
 
 . ./test-lib.sh
 
-if ! test_have_prereq WITHOUT_BREAKING_CHANGES
+if test_have_prereq WITH_BREAKING_CHANGES
 then
 	skip_all='skipping git-pack-redundant tests; built with breaking changes'
 	test_done

t/t5505-remote.sh

@@ -1123,7 +1123,7 @@ Pull: refs/heads/main:refs/heads/origin
 Pull: refs/heads/next:refs/heads/origin2
 EOF
 
-test_expect_success WITHOUT_BREAKING_CHANGES 'migrate a remote from named file in $GIT_DIR/remotes' '
+test_expect_success !WITH_BREAKING_CHANGES 'migrate a remote from named file in $GIT_DIR/remotes' '
 	git clone one five &&
 	origin_url=$(pwd)/one &&
 	(
@@ -1149,7 +1149,7 @@ test_expect_success WITHOUT_BREAKING_CHANGES 'migrate a remote from named file i
 	)
 '
 
-test_expect_success WITHOUT_BREAKING_CHANGES 'migrate a remote from named file in $GIT_DIR/branches' '
+test_expect_success !WITH_BREAKING_CHANGES 'migrate a remote from named file in $GIT_DIR/branches' '
 	git clone --template= one six &&
 	origin_url=$(pwd)/one &&
 	(
@@ -1165,7 +1165,7 @@ test_expect_success WITHOUT_BREAKING_CHANGES 'migrate a remote from named file i
 	)
 '
 
-test_expect_success WITHOUT_BREAKING_CHANGES 'migrate a remote from named file in $GIT_DIR/branches (2)' '
+test_expect_success !WITH_BREAKING_CHANGES 'migrate a remote from named file in $GIT_DIR/branches (2)' '
 	git clone --template= one seven &&
 	(
 		cd seven &&

t/t5515-fetch-merge-logic.sh

@@ -104,7 +104,7 @@ test_expect_success setup '
 	git config remote.config-glob.fetch refs/heads/*:refs/remotes/rem/* &&
 	remotes="$remotes config-glob" &&
 
-	if test_have_prereq WITHOUT_BREAKING_CHANGES
+	if ! test_have_prereq WITH_BREAKING_CHANGES
 	then
 		mkdir -p .git/remotes &&
 		cat >.git/remotes/remote-explicit <<-\EOF &&

t/t5516-fetch-push.sh

@@ -975,7 +975,7 @@ test_expect_success 'allow push to HEAD of non-bare repository (config)' '
 	! grep "warning: updating the current branch" stderr
 '
 
-test_expect_success WITHOUT_BREAKING_CHANGES 'fetch with branches' '
+test_expect_success !WITH_BREAKING_CHANGES 'fetch with branches' '
 	mk_empty testrepo &&
 	git branch second $the_first_commit &&
 	git checkout second &&
@@ -991,7 +991,7 @@ test_expect_success WITHOUT_BREAKING_CHANGES 'fetch with branches' '
 	git checkout main
 '
 
-test_expect_success WITHOUT_BREAKING_CHANGES 'fetch with branches containing #' '
+test_expect_success !WITH_BREAKING_CHANGES 'fetch with branches containing #' '
 	mk_empty testrepo &&
 	mkdir testrepo/.git/branches &&
 	echo "..#second" > testrepo/.git/branches/branch2 &&
@@ -1005,7 +1005,7 @@ test_expect_success WITHOUT_BREAKING_CHANGES 'fetch with branches containing #'
 	git checkout main
 '
 
-test_expect_success WITHOUT_BREAKING_CHANGES 'push with branches' '
+test_expect_success !WITH_BREAKING_CHANGES 'push with branches' '
 	mk_empty testrepo &&
 	git checkout second &&
 
@@ -1022,7 +1022,7 @@ test_expect_success WITHOUT_BREAKING_CHANGES 'push with branches' '
 	)
 '
 
-test_expect_success WITHOUT_BREAKING_CHANGES 'push with branches containing #' '
+test_expect_success !WITH_BREAKING_CHANGES 'push with branches containing #' '
 	mk_empty testrepo &&
 
 	test_when_finished "rm -rf .git/branches" &&

t/test-lib.sh

@@ -1862,8 +1862,13 @@ test_lazy_prereq CURL '
 	curl --version
 '
 
+test_lazy_prereq WITH_BREAKING_CHANGES '
+	test -n "$WITH_BREAKING_CHANGES"
+'
+
 test_lazy_prereq WITHOUT_BREAKING_CHANGES '
-	test -z "$WITH_BREAKING_CHANGES"
+	# Signal that this prereq should not be used.
+	exit 125
 '
 
 # SHA1 is a test if the hash algorithm in use is SHA-1.  This is both for tests