tests: index::version: add test to read index version v4

While we have a simple test to determine whether we can write an index
of version 4, we never verified that we are able to read this kind of
index (and in fact, we were not able to do so). Add a new repository
which has an index of version 4. This repository is then read from a new
test.
diff --git a/tests/index/version.c b/tests/index/version.c
index 688a20f..c3cb0cd 100644
--- a/tests/index/version.c
+++ b/tests/index/version.c
@@ -9,6 +9,29 @@
         g_repo = NULL;
 }
 
+void test_index_version__can_read_v4(void)
+{
+	const char *paths[] = {
+	    "file.tx", "file.txt", "file.txz", "foo", "zzz",
+	};
+	git_index *index;
+	size_t i;
+
+	g_repo = cl_git_sandbox_init("indexv4");
+
+	cl_git_pass(git_repository_index(&index, g_repo));
+	cl_assert_equal_sz(git_index_entrycount(index), 5);
+
+	for (i = 0; i < ARRAY_SIZE(paths); i++) {
+		const git_index_entry *entry =
+		    git_index_get_bypath(index, paths[i], GIT_INDEX_STAGE_NORMAL);
+
+		cl_assert(entry != NULL);
+	}
+
+	git_index_free(index);
+}
+
 void test_index_version__can_write_v4(void)
 {
 	git_index *index;
diff --git a/tests/resources/indexv4/.gitted/HEAD b/tests/resources/indexv4/.gitted/HEAD
new file mode 100644
index 0000000..cb089cd
--- /dev/null
+++ b/tests/resources/indexv4/.gitted/HEAD
@@ -0,0 +1 @@
+ref: refs/heads/master
diff --git a/tests/resources/indexv4/.gitted/config b/tests/resources/indexv4/.gitted/config
new file mode 100644
index 0000000..515f483
--- /dev/null
+++ b/tests/resources/indexv4/.gitted/config
@@ -0,0 +1,5 @@
+[core]
+	repositoryformatversion = 0
+	filemode = true
+	bare = false
+	logallrefupdates = true
diff --git a/tests/resources/indexv4/.gitted/index b/tests/resources/indexv4/.gitted/index
new file mode 100644
index 0000000..e8fc617
--- /dev/null
+++ b/tests/resources/indexv4/.gitted/index
Binary files differ
diff --git a/tests/resources/indexv4/.gitted/objects/4c/9109b3e671d851eec87e0e72f6305b582e7e99 b/tests/resources/indexv4/.gitted/objects/4c/9109b3e671d851eec87e0e72f6305b582e7e99
new file mode 100644
index 0000000..cedd594
--- /dev/null
+++ b/tests/resources/indexv4/.gitted/objects/4c/9109b3e671d851eec87e0e72f6305b582e7e99
Binary files differ
diff --git a/tests/resources/indexv4/.gitted/objects/b0/952dbb50bed5f01e03e31b296184cb183e54a7 b/tests/resources/indexv4/.gitted/objects/b0/952dbb50bed5f01e03e31b296184cb183e54a7
new file mode 100644
index 0000000..0ddc1d1
--- /dev/null
+++ b/tests/resources/indexv4/.gitted/objects/b0/952dbb50bed5f01e03e31b296184cb183e54a7
Binary files differ
diff --git a/tests/resources/indexv4/.gitted/objects/e6/9de29bb2d1d6434b8b29ae775ad8c2e48c5391 b/tests/resources/indexv4/.gitted/objects/e6/9de29bb2d1d6434b8b29ae775ad8c2e48c5391
new file mode 100644
index 0000000..7112238
--- /dev/null
+++ b/tests/resources/indexv4/.gitted/objects/e6/9de29bb2d1d6434b8b29ae775ad8c2e48c5391
Binary files differ
diff --git a/tests/resources/indexv4/.gitted/refs/heads/master b/tests/resources/indexv4/.gitted/refs/heads/master
new file mode 100644
index 0000000..f3e960e
--- /dev/null
+++ b/tests/resources/indexv4/.gitted/refs/heads/master
@@ -0,0 +1 @@
+b0952dbb50bed5f01e03e31b296184cb183e54a7
diff --git a/tests/resources/indexv4/file.tx b/tests/resources/indexv4/file.tx
new file mode 100644
index 0000000..e69de29
--- /dev/null
+++ b/tests/resources/indexv4/file.tx
diff --git a/tests/resources/indexv4/file.txt b/tests/resources/indexv4/file.txt
new file mode 100644
index 0000000..e69de29
--- /dev/null
+++ b/tests/resources/indexv4/file.txt
diff --git a/tests/resources/indexv4/file.txz b/tests/resources/indexv4/file.txz
new file mode 100644
index 0000000..e69de29
--- /dev/null
+++ b/tests/resources/indexv4/file.txz
diff --git a/tests/resources/indexv4/foo b/tests/resources/indexv4/foo
new file mode 100644
index 0000000..e69de29
--- /dev/null
+++ b/tests/resources/indexv4/foo
diff --git a/tests/resources/indexv4/zzz b/tests/resources/indexv4/zzz
new file mode 100644
index 0000000..e69de29
--- /dev/null
+++ b/tests/resources/indexv4/zzz