clone: test for our behavior on odd objects/* content

Add tests for what happens when we perform a local clone on a repo
containing odd files at .git/object directory, such as symlinks to other
dirs, or unknown files.

I'm bending over backwards here to avoid a SHA-1 dependency. See [1]
for an earlier and simpler version that hardcoded SHA-1s.

This behavior has been the same for a *long* time, but hasn't been
tested for.

There's a good post-hoc argument to be made for copying over unknown
things, e.g. I'd like a git version that doesn't know about the
commit-graph to copy it under "clone --local" so a newer git version
can make use of it.

In follow-up commits we'll look at changing some of this behavior, but
for now, let's just assert it as-is so we'll notice what we'll change
later.

1. https://public-inbox.org/git/20190226002625.13022-5-avarab@gmail.com/

Signed-off-by: Ævar Arnfjörð Bjarmason <avarab@gmail.com>
[matheus.bernardino: improved and split tests in more than one patch]
Helped-by: Matheus Tavares <matheus.bernardino@usp.br>
Signed-off-by: Matheus Tavares <matheus.bernardino@usp.br>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

t/t5604-clone-reference.sh

@@ -221,4 +221,115 @@ test_expect_success 'clone, dissociate from alternates' '
 	( cd C && git fsck )
 '
 
+test_expect_success 'setup repo with garbage in objects/*' '
+	git init S &&
+	(
+		cd S &&
+		test_commit A &&
+
+		cd .git/objects &&
+		>.some-hidden-file &&
+		>some-file &&
+		mkdir .some-hidden-dir &&
+		>.some-hidden-dir/some-file &&
+		>.some-hidden-dir/.some-dot-file &&
+		mkdir some-dir &&
+		>some-dir/some-file &&
+		>some-dir/.some-dot-file
+	)
+'
+
+test_expect_success 'clone a repo with garbage in objects/*' '
+	for option in --local --no-hardlinks --shared --dissociate
+	do
+		git clone $option S S$option || return 1 &&
+		git -C S$option fsck || return 1
+	done &&
+	find S-* -name "*some*" | sort >actual &&
+	cat >expected <<-EOF &&
+	S--dissociate/.git/objects/.some-hidden-file
+	S--dissociate/.git/objects/some-dir
+	S--dissociate/.git/objects/some-dir/.some-dot-file
+	S--dissociate/.git/objects/some-dir/some-file
+	S--dissociate/.git/objects/some-file
+	S--local/.git/objects/.some-hidden-file
+	S--local/.git/objects/some-dir
+	S--local/.git/objects/some-dir/.some-dot-file
+	S--local/.git/objects/some-dir/some-file
+	S--local/.git/objects/some-file
+	S--no-hardlinks/.git/objects/.some-hidden-file
+	S--no-hardlinks/.git/objects/some-dir
+	S--no-hardlinks/.git/objects/some-dir/.some-dot-file
+	S--no-hardlinks/.git/objects/some-dir/some-file
+	S--no-hardlinks/.git/objects/some-file
+	EOF
+	test_cmp expected actual
+'
+
+test_expect_success SYMLINKS 'setup repo with manually symlinked dirs and unknown files at objects/' '
+	git init T &&
+	(
+		cd T &&
+		git config gc.auto 0 &&
+		test_commit A &&
+		git gc &&
+		test_commit B &&
+
+		cd .git/objects &&
+		mv pack packs &&
+		ln -s packs pack &&
+		find ?? -type d >loose-dirs &&
+		last_loose=$(tail -n 1 loose-dirs) &&
+		rm -f loose-dirs &&
+		mv $last_loose a-loose-dir &&
+		ln -s a-loose-dir $last_loose &&
+		find . -type f | sort >../../../T.objects-files.raw &&
+		echo unknown_content >unknown_file
+	) &&
+	git -C T fsck &&
+	git -C T rev-list --all --objects >T.objects
+'
+
+
+test_expect_success SYMLINKS 'clone repo with symlinked dirs and unknown files at objects/' '
+	for option in --local --no-hardlinks --shared --dissociate
+	do
+		git clone $option T T$option || return 1 &&
+		git -C T$option fsck || return 1 &&
+		git -C T$option rev-list --all --objects >T$option.objects &&
+		test_cmp T.objects T$option.objects &&
+		(
+			cd T$option/.git/objects &&
+			find . -type f | sort >../../../T$option.objects-files.raw
+		)
+	done &&
+
+	for raw in $(ls T*.raw)
+	do
+		sed -e "s!/../!/Y/!; s![0-9a-f]\{38,\}!Z!" -e "/commit-graph/d" \
+		    -e "/multi-pack-index/d" <$raw >$raw.de-sha || return 1
+	done &&
+
+	cat >expected-files <<-EOF &&
+	./Y/Z
+	./Y/Z
+	./a-loose-dir/Z
+	./Y/Z
+	./info/packs
+	./pack/pack-Z.idx
+	./pack/pack-Z.pack
+	./packs/pack-Z.idx
+	./packs/pack-Z.pack
+	./unknown_file
+	EOF
+
+	for option in --local --dissociate --no-hardlinks
+	do
+		test_cmp expected-files T$option.objects-files.raw.de-sha || return 1
+	done &&
+
+	echo ./info/alternates >expected-files &&
+	test_cmp expected-files T--shared.objects-files.raw
+'
+
 test_done