bundle tests: use test_cmp instead of grep

Change the bundle tests to fully compare the expected "git ls-remote"
or "git bundle list-heads" output, instead of merely grepping it.

This avoids subtle regressions in the tests. In
f62e0a39b6 (t5704 (bundle): add tests for bundle --stdin, 2010-04-19)
the "bundle --stdin <rev-list options>" test was added to make sure we
didn't include the tag.

But since the --stdin mode didn't work until 5bb0fd2cab (bundle:
arguments can be read from stdin, 2021-01-11) our grepping of
"master" (later "main") missed the important part of the test.

Namely that we should not include the "refs/tags/tag" tag in that
case. Since the test only grepped for "main" in the output we'd miss a
regression in that code.

So let's use test_cmp instead, and also in the other nearby tests
where it's easy.

This does make things a bit more verbose in the case of the test
that's checking the bundle header, since it's different under SHA1 and
SHA256. I think this makes test easier to follow.

I've got some WIP changes to extend the "git bundle" command to dump
parts of the header out, which are easier to understand if we test the
output explicitly like this.

Signed-off-by: Ævar Arnfjörð Bjarmason <avarab@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

t/t5607-clone-bundle.sh

@@ -29,11 +29,21 @@ test_expect_success '"verify" needs a worktree' '
 
 test_expect_success 'annotated tags can be excluded by rev-list options' '
 	git bundle create bundle --all --since=7.Apr.2005.15:14:00.-0700 &&
-	git ls-remote bundle > output &&
-	grep tag output &&
+	cat >expect <<-EOF &&
+	$(git rev-parse HEAD)	HEAD
+	$(git rev-parse tag)	refs/tags/tag
+	$(git rev-parse main)	refs/heads/main
+	EOF
+	git ls-remote bundle >actual &&
+	test_cmp expect actual &&
+
 	git bundle create bundle --all --since=7.Apr.2005.15:16:00.-0700 &&
-	git ls-remote bundle > output &&
-	! grep tag output
+	cat >expect <<-EOF &&
+	$(git rev-parse HEAD)	HEAD
+	$(git rev-parse main)	refs/heads/main
+	EOF
+	git ls-remote bundle >actual &&
+	test_cmp expect actual
 '
 
 test_expect_success 'die if bundle file cannot be created' '
@@ -43,14 +53,20 @@ test_expect_success 'die if bundle file cannot be created' '
 
 test_expect_success 'bundle --stdin' '
 	echo main | git bundle create stdin-bundle.bdl --stdin &&
-	git ls-remote stdin-bundle.bdl >output &&
-	grep main output
+	cat >expect <<-EOF &&
+	$(git rev-parse main)	refs/heads/main
+	EOF
+	git ls-remote stdin-bundle.bdl >actual &&
+	test_cmp expect actual
 '
 
 test_expect_success 'bundle --stdin <rev-list options>' '
 	echo main | git bundle create hybrid-bundle.bdl --stdin tag &&
-	git ls-remote hybrid-bundle.bdl >output &&
-	grep main output
+	cat >expect <<-EOF &&
+	$(git rev-parse main)	refs/heads/main
+	EOF
+	git ls-remote stdin-bundle.bdl >actual &&
+	test_cmp expect actual
 '
 
 test_expect_success 'empty bundle file is rejected' '
@@ -67,11 +83,31 @@ test_expect_success 'ridiculously long subject in boundary' '
 	printf "%01200d\n" 0 | git commit -F - &&
 	test_commit fifth &&
 	git bundle create long-subject-bundle.bdl HEAD^..HEAD &&
-	git bundle list-heads long-subject-bundle.bdl >heads &&
-	test -s heads &&
+	cat >expect <<-EOF &&
+	$(git rev-parse main) HEAD
+	EOF
+	git bundle list-heads long-subject-bundle.bdl >actual &&
+	test_cmp expect actual &&
+
 	git fetch long-subject-bundle.bdl &&
-	sed -n "/^-/{p;q;}" long-subject-bundle.bdl >boundary &&
-	grep "^-$OID_REGEX " boundary
+
+	if ! test_have_prereq SHA1
+	then
+		echo "@object-format=sha256"
+	fi >expect &&
+	cat >>expect <<-EOF &&
+	-$(git log --pretty=format:"%H %s" -1 HEAD^)
+	$(git rev-parse HEAD) HEAD
+	EOF
+
+	if test_have_prereq SHA1
+	then
+		head -n 3 long-subject-bundle.bdl
+	else
+		head -n 4 long-subject-bundle.bdl
+	fi | grep -v "^#" >actual &&
+
+	test_cmp expect actual
 '
 
 test_expect_success 'prerequisites with an empty commit message' '
@@ -103,7 +139,11 @@ test_expect_success 'fetch SHA-1 from bundle' '
 
 test_expect_success 'git bundle uses expected default format' '
 	git bundle create bundle HEAD^.. &&
-	head -n1 bundle | grep "^# v$(test_oid version) git bundle$"
+	cat >expect <<-EOF &&
+	# v$(test_oid version) git bundle
+	EOF
+	head -n1 bundle >actual &&
+	test_cmp expect actual
 '
 
 test_expect_success 'git bundle v3 has expected contents' '