t3436: check --committer-date-is-author-date result more carefully

After running "rebase --committer-date-is-author-date", we confirm that
the committer date is the same as the author date. However, we don't
look at any other parts of the committer ident line to make sure we
didn't screw them up. And indeed, there are a few bugs here. Depending
on the rebase backend in use, we may accidentally use the author email
instead of the committer's, or even an empty string.

Let's teach our test_ctime_is_atime helper to check the committer name
and email, which reveals several failing tests.

Signed-off-by: Jeff King <peff@peff.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

t/t3436-rebase-more-options.sh

@@ -65,31 +65,31 @@ test_expect_success '--ignore-whitespace is remembered when continuing' '
 '
 
 test_ctime_is_atime () {
-	git log $1 --format=%ai >authortime &&
-	git log $1 --format=%ci >committertime &&
+	git log $1 --format="$GIT_COMMITTER_NAME <$GIT_COMMITTER_EMAIL> %ai" >authortime &&
+	git log $1 --format="%cn <%ce> %ci" >committertime &&
 	test_cmp authortime committertime
 }
 
-test_expect_success '--committer-date-is-author-date works with apply backend' '
+test_expect_failure '--committer-date-is-author-date works with apply backend' '
 	GIT_AUTHOR_DATE="@1234 +0300" git commit --amend --reset-author &&
 	git rebase --apply --committer-date-is-author-date HEAD^ &&
 	test_ctime_is_atime -1
 '
 
-test_expect_success '--committer-date-is-author-date works with merge backend' '
+test_expect_failure '--committer-date-is-author-date works with merge backend' '
 	GIT_AUTHOR_DATE="@1234 +0300" git commit --amend --reset-author &&
 	git rebase -m --committer-date-is-author-date HEAD^ &&
 	test_ctime_is_atime -1
 '
 
-test_expect_success '--committer-date-is-author-date works with rebase -r' '
+test_expect_failure '--committer-date-is-author-date works with rebase -r' '
 	git checkout side &&
 	GIT_AUTHOR_DATE="@1234 +0300" git merge --no-ff commit3 &&
 	git rebase -r --root --committer-date-is-author-date &&
 	test_ctime_is_atime
 '
 
-test_expect_success '--committer-date-is-author-date works when forking merge' '
+test_expect_failure '--committer-date-is-author-date works when forking merge' '
 	git checkout side &&
 	GIT_AUTHOR_DATE="@1234 +0300" git merge --no-ff commit3 &&
 	PATH="./test-bin:$PATH" git rebase -r --root --strategy=test \
@@ -145,7 +145,7 @@ test_expect_success '--reset-author-date works with rebase -r' '
 	test_atime_is_ignored
 '
 
-test_expect_success '--reset-author-date with --committer-date-is-author-date works' '
+test_expect_failure '--reset-author-date with --committer-date-is-author-date works' '
 	test_must_fail git rebase -m --committer-date-is-author-date \
 		--reset-author-date --onto commit2^^ commit2^ commit3 &&
 	git checkout --theirs foo &&