rebase --apply: restore some tests

980b482d28 ("rebase tests: mark tests specific to the am-backend with
--am", 2020-02-15) sought to prepare tests testing the "apply" backend
in preparation for 2ac0d6273f ("rebase: change the default backend
from "am" to "merge"", 2020-02-15). However some tests seem to have
been missed leading to us testing the "merge" backend twice. This
patch fixes some cases that I noticed while adding tests to these
files, I have not audited all the other rebase test files. I've
reworded a couple of the test descriptions to make it clear which
backend they are testing.

Signed-off-by: Phillip Wood <phillip.wood@dunelm.org.uk>
Reviewed-by: Elijah Newren <newren@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

t/t3403-rebase-skip.sh

@@ -52,7 +52,7 @@ test_expect_success setup '
 	'
 
 test_expect_success 'rebase with git am -3 (default)' '
-	test_must_fail git rebase main
+	test_must_fail git rebase --apply main
 '
 
 test_expect_success 'rebase --skip can not be used with other options' '

t/t3418-rebase-continue.sh

@@ -21,7 +21,7 @@ test_expect_success 'setup' '
 	git checkout main
 '
 
-test_expect_success 'interactive rebase --continue works with touched file' '
+test_expect_success 'merge based rebase --continue with works with touched file' '
 	rm -fr .git/rebase-* &&
 	git reset --hard &&
 	git checkout main &&
@@ -31,12 +31,12 @@ test_expect_success 'interactive rebase --continue works with touched file' '
 	git rebase --continue
 '
 
-test_expect_success 'non-interactive rebase --continue works with touched file' '
+test_expect_success 'apply based rebase --continue works with touched file' '
 	rm -fr .git/rebase-* &&
 	git reset --hard &&
 	git checkout main &&
 
-	test_must_fail git rebase --onto main main topic &&
+	test_must_fail git rebase --apply --onto main main topic &&
 	echo "Resolved" >F2 &&
 	git add F2 &&
 	test-tool chmtime =-60 F1 &&
@@ -254,7 +254,7 @@ test_rerere_autoupdate () {
 	'
 }
 
-test_rerere_autoupdate
+test_rerere_autoupdate --apply
 test_rerere_autoupdate -m
 GIT_SEQUENCE_EDITOR=: && export GIT_SEQUENCE_EDITOR
 test_rerere_autoupdate -i