t7502: narrow checks for author/committer name in template

t7502.20 and t7502.21 check that the author and committer
name are mentioned in the commit message template under
certain circumstances. However, they end up checking a much
larger and unnecessary portion of the template. Let's narrow
their checks to the specific lines.

While we're at it, let's give these tests more descriptive
names, so their purposes are more obvious.

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

t/t7502-commit.sh

@@ -235,24 +235,15 @@ test_expect_success 'cleanup commit messages (strip,-F,-e): output' '
 	test_i18ncmp expect actual
 '
 
-echo "#
-# Author:    $GIT_AUTHOR_NAME <$GIT_AUTHOR_EMAIL>
-#" >> expect
-
-test_expect_success 'author different from committer' '
+test_expect_success 'message shows author when it is not equal to committer' '
 	echo >>negative &&
 	test_might_fail git commit -e -m "sample" &&
-	head -n 7 .git/COMMIT_EDITMSG >actual &&
-	test_i18ncmp expect actual
+	test_i18ngrep \
+	  "^# Author: *A U Thor <author@example.com>\$" \
+	  .git/COMMIT_EDITMSG
 '
 
-mv expect expect.tmp
-sed '$d' < expect.tmp > expect
-rm -f expect.tmp
-echo "# Committer:
-#" >> expect
-
-test_expect_success 'committer is automatic' '
+test_expect_success 'message shows committer when it is automatic' '
 
 	echo >>negative &&
 	(
@@ -261,9 +252,9 @@ test_expect_success 'committer is automatic' '
 		# must fail because there is no change
 		test_must_fail git commit -e -m "sample"
 	) &&
-	head -n 8 .git/COMMIT_EDITMSG |	\
-	sed "s/^# Committer: .*/# Committer:/" >actual
-	test_i18ncmp expect actual
+	# the ident is calculated from the system, so we cannot
+	# check the actual value, only that it is there
+	test_i18ngrep "^# Committer: " .git/COMMIT_EDITMSG
 '
 
 write_script .git/FAKE_EDITOR <<EOF