tests: remote: add test suite to test listing remotes

There was a bug when calling `git_remote_list` that caused us to not
re-read modified configurations when using `git_config_iterator`. This
bug also impacted `git_remote_list`, which thus failed to provide an
up-to-date list of remotes. Add a test suite remote::list with a single
test that verifies we do the right thing.

tests/remote/list.c

+#include "clar_libgit2.h"
+#include "config/config_helpers.h"
+
+static git_repository *_repo;
+
+#define TEST_URL "http://github.com/libgit2/libgit2.git"
+
+void test_remote_list__initialize(void)
+{
+	_repo = cl_git_sandbox_init("testrepo");
+}
+
+void test_remote_list__cleanup(void)
+{
+	cl_git_sandbox_cleanup();
+}
+
+void test_remote_list__always_checks_disk_config(void)
+{
+	git_repository *repo;
+	git_strarray remotes;
+	git_remote *remote;
+
+	cl_git_pass(git_repository_open(&repo, git_repository_path(_repo)));
+
+	cl_git_pass(git_remote_list(&remotes, _repo));
+	cl_assert_equal_sz(remotes.count, 1);
+	git_strarray_free(&remotes);
+
+	cl_git_pass(git_remote_create(&remote, _repo, "valid-name", TEST_URL));
+
+	cl_git_pass(git_remote_list(&remotes, _repo));
+	cl_assert_equal_sz(remotes.count, 2);
+	git_strarray_free(&remotes);
+
+	cl_git_pass(git_remote_list(&remotes, repo));
+	cl_assert_equal_sz(remotes.count, 2);
+	git_strarray_free(&remotes);
+
+	git_repository_free(repo);
+	git_remote_free(remote);
+}
+