thodg/libgit2

diff --git a/src/submodule.c b/src/submodule.c
index 913c97a..24f250a 100644
--- a/src/submodule.c
+++ b/src/submodule.c
@@ -91,8 +91,10 @@ static int submodule_cache_init(git_repository *repo, int refresh);
 static void submodule_cache_free(git_submodule_cache *cache);
 
 static git_config_backend *open_gitmodules(git_submodule_cache *, int gitmod);
-static int lookup_head_remote_key(git_buf *key, git_repository *repo);
-static int lookup_head_remote(git_buf *url, git_repository *repo);
+static int get_url_base(git_buf *url, git_repository *repo);
+static int lookup_default_remote(git_remote **remote, git_repository *repo);
+static int lookup_head_remote_key(git_buf *remote_key, git_repository *repo);
+static int lookup_head_remote(git_remote **remote, git_repository *repo);
 static int submodule_get(git_submodule **, git_submodule_cache *, const char *, const char *);
 static int submodule_load_from_config(const git_config_entry *, void *);
 static int submodule_load_from_wd_lite(git_submodule *);
@@ -644,7 +646,7 @@ int git_submodule_resolve_url(git_buf *out, git_repository *repo, const char *ur
 	assert(url);
 
 	if (git_path_is_relative(url)) {
-		if (!(error = lookup_head_remote(out, repo)))
+		if (!(error = get_url_base(out, repo)))
 			error = git_path_apply_relative(out, url);
 	} else if (strchr(url, ':') != NULL || url[0] == '/') {
 		error = git_buf_sets(out, url);
@@ -1795,81 +1797,109 @@ static int submodule_cache_init(git_repository *repo, int cache_refresh)
 	return error;
 }
 
-static int lookup_head_remote_key(git_buf *key, git_repository *repo)
+static int get_url_base(git_buf *url, git_repository *repo)
 {
 	int error;
-	git_config *cfg;
-	git_reference *head = NULL, *remote = NULL;
-	const char *tgt, *scan;
+	git_remote *remote;
+	error = lookup_default_remote(&remote, repo);
+	const char *url_ptr;
+
+	assert(url && repo);
+	
+	if (!error)	{
+		url_ptr = git_remote_url(remote);
+	} else if (error == GIT_ENOTFOUND) {
+		/* if repository does not have a default remote, use workdir instead */
+		giterr_clear();
+		error = 0;
+		url_ptr = git_repository_workdir(repo);
+	}
+	
+	if (error < 0)
+		goto cleanup;
+		
+	error = git_buf_sets(url, url_ptr);
 
-	/* 1. resolve HEAD -> refs/heads/BRANCH
-	 * 2. lookup config branch.BRANCH.remote -> ORIGIN
-	 * 3. return remote.ORIGIN.url
-	 */
+cleanup:
+	git_remote_free(remote);
 
-	git_buf_clear(key);
+	return error;
+}
 
-	if ((error = git_repository_config__weakptr(&cfg, repo)) < 0)
-		return error;
+/**
+ * Lookup the remote that is considered the default remote in the current state
+ */
+static int lookup_default_remote(git_remote **remote, git_repository *repo)
+{
+	int error;
+	error = lookup_head_remote(remote, repo);
 
-	if (git_reference_lookup(&head, repo, GIT_HEAD_FILE) < 0) {
-		giterr_set(GITERR_SUBMODULE,
-			"Cannot resolve relative URL when HEAD cannot be resolved");
-		return GIT_ENOTFOUND;
+	assert(remote && repo);
+
+	// if that failed, use 'origin' instead
+	if (error == GIT_ENOTFOUND) {
+		error = git_remote_load(remote, repo, "origin");
 	}
 
-	if (git_reference_type(head) != GIT_REF_SYMBOLIC) {
+	if (error == GIT_ENOTFOUND) {
 		giterr_set(GITERR_SUBMODULE,
-			"Cannot resolve relative URL when HEAD is not symbolic");
-		error = GIT_ENOTFOUND;
-		goto cleanup;
+			"Neither HEAD points to a local tracking branch, nor does origin exist");
 	}
 
-	if ((error = git_branch_upstream(&remote, head)) < 0)
-		goto cleanup;
+	return error;
+}
 
-	/* remote should refer to something like refs/remotes/ORIGIN/BRANCH */
+/**
+ * Lookup name of remote of the local tracking branch HEAD points to
+ */
+static int lookup_head_remote_key(git_buf *remote_name, git_repository *repo)
+{
+	int error;
+	git_reference *head = NULL;
+	git_buf upstream_name = GIT_BUF_INIT;
 
-	if (git_reference_type(remote) != GIT_REF_SYMBOLIC ||
-		git__prefixcmp(
-			git_reference_symbolic_target(remote), GIT_REFS_REMOTES_DIR) != 0)
-	{
-		giterr_set(GITERR_SUBMODULE,
-			"Cannot resolve relative URL when HEAD is not symbolic");
-		error = GIT_ENOTFOUND;
-		goto cleanup;
-	}
+	/* lookup and dereference HEAD */
+	if ((error = git_repository_head(&head, repo) < 0))
+	   goto cleanup;
 
-	scan = tgt = git_reference_symbolic_target(remote) +
-		strlen(GIT_REFS_REMOTES_DIR);
-	while (*scan && (*scan != '/' || (scan > tgt && scan[-1] != '\\')))
-		scan++; /* find non-escaped slash to end ORIGIN name */
+	/* lookup remote tracking branch of HEAD */
+	if ((error = git_branch_upstream_name(&upstream_name, repo, git_reference_name(head))) < 0)
+		goto cleanup;
 
-	error = git_buf_printf(key, "remote.%.*s.url", (int)(scan - tgt), tgt);
+	/* lookup remote of remote tracking branch */
+	if ((error = git_branch_remote_name(remote_name, repo, upstream_name.ptr)) < 0)
+		goto cleanup;
 
 cleanup:
-	if (error < 0)
-		git_buf_clear(key);
-
-	git_reference_free(head);
-	git_reference_free(remote);
+	git_buf_free(&upstream_name);
+	if (head)
+		git_reference_free(head);
 
 	return error;
 }
 
-static int lookup_head_remote(git_buf *url, git_repository *repo)
+/**
+ * Lookup the remote of the local tracking branch HEAD points to
+ */
+static int lookup_head_remote(git_remote **remote, git_repository *repo)
 {
 	int error;
-	git_config *cfg;
-	const char *tgt;
-	git_buf key = GIT_BUF_INIT;
+	git_buf remote_name = GIT_BUF_INIT;
 
-	if (!(error = lookup_head_remote_key(&key, repo)) &&
-		!(error = git_repository_config__weakptr(&cfg, repo)) &&
-		!(error = git_config_get_string(&tgt, cfg, key.ptr)))
-		error = git_buf_sets(url, tgt);
+	assert(remote && repo);
+
+	/* should be NULL in case of error */
+	*remote = NULL;
+
+	/* lookup remote of remote tracking branch name */
+	if ((error = lookup_head_remote_key(&remote_name, repo)) < 0)
+		goto cleanup;
+
+	error = git_remote_load(remote, repo, remote_name.ptr);
+
+cleanup:
+	git_buf_free(&remote_name);
 
-	git_buf_free(&key);
 	return error;
 }
 
diff --git a/tests/submodule/add.c b/tests/submodule/add.c
new file mode 100644
index 0000000..2d51b3d
--- /dev/null
+++ b/tests/submodule/add.c
@@ -0,0 +1,115 @@
+#include "clar_libgit2.h"
+#include "posix.h"
+#include "path.h"
+#include "submodule_helpers.h"
+
+static git_repository *g_repo = NULL;
+
+static void assert_submodule_url(const char* name, const char *url);
+
+void test_submodule_add__cleanup(void)
+{
+	cl_git_sandbox_cleanup();
+}
+
+void test_submodule_add__url_absolute(void)
+{
+	g_repo = setup_fixture_submod2();
+	git_submodule *sm;
+
+	/* re-add existing submodule */
+	cl_assert_equal_i(
+		GIT_EEXISTS,
+		git_submodule_add_setup(NULL, g_repo, "whatever", "sm_unchanged", 1));
+
+	/* add a submodule using a gitlink */
+
+	cl_git_pass(
+		git_submodule_add_setup(&sm, g_repo, "https://github.com/libgit2/libgit2.git", "sm_libgit2", 1)
+		);
+	git_submodule_free(sm);
+
+	cl_assert(git_path_isfile("submod2/" "sm_libgit2" "/.git"));
+
+	cl_assert(git_path_isdir("submod2/.git/modules"));
+	cl_assert(git_path_isdir("submod2/.git/modules/" "sm_libgit2"));
+	cl_assert(git_path_isfile("submod2/.git/modules/" "sm_libgit2" "/HEAD"));
+	assert_submodule_url("sm_libgit2", "https://github.com/libgit2/libgit2.git");
+
+	/* add a submodule not using a gitlink */
+
+	cl_git_pass(
+		git_submodule_add_setup(&sm, g_repo, "https://github.com/libgit2/libgit2.git", "sm_libgit2b", 0)
+		);
+	git_submodule_free(sm);
+
+	cl_assert(git_path_isdir("submod2/" "sm_libgit2b" "/.git"));
+	cl_assert(git_path_isfile("submod2/" "sm_libgit2b" "/.git/HEAD"));
+	cl_assert(!git_path_exists("submod2/.git/modules/" "sm_libgit2b"));
+	assert_submodule_url("sm_libgit2b", "https://github.com/libgit2/libgit2.git");
+}
+
+void test_submodule_add__url_relative(void) {
+	git_submodule *sm;
+	git_remote *remote;
+	
+	/* default remote url is https://github.com/libgit2/false.git */
+	g_repo = cl_git_sandbox_init("testrepo2");
+	
+	/* make sure we're not defaulting to origin - rename origin -> test_remote */
+	cl_git_pass(git_remote_load(&remote, g_repo, "origin"));
+	cl_git_pass(git_remote_rename(remote, "test_remote", NULL, NULL));
+	cl_git_fail(git_remote_load(&remote, g_repo, "origin"));
+	git_remote_free(remote);
+
+	cl_git_pass(
+		git_submodule_add_setup(&sm, g_repo, "../TestGitRepository", "TestGitRepository", 1)
+		);
+	git_submodule_free(sm);
+		
+	assert_submodule_url("TestGitRepository", "https://github.com/libgit2/TestGitRepository");
+}
+
+void test_submodule_add__url_relative_to_origin(void) {
+	git_submodule *sm;
+	
+	/* default remote url is https://github.com/libgit2/false.git */
+	g_repo = cl_git_sandbox_init("testrepo2");
+
+	cl_git_pass(
+		git_submodule_add_setup(&sm, g_repo, "../TestGitRepository", "TestGitRepository", 1)
+		);
+	git_submodule_free(sm);
+		
+	assert_submodule_url("TestGitRepository", "https://github.com/libgit2/TestGitRepository");
+}
+
+void test_submodule_add__url_relative_to_workdir(void) {
+	git_submodule *sm;
+
+	/* In this repo, HEAD (master) has no remote tracking branc h*/
+	g_repo = cl_git_sandbox_init("testrepo");
+
+	cl_git_pass(
+		git_submodule_add_setup(&sm, g_repo, "./", "TestGitRepository", 1)
+		);
+	git_submodule_free(sm);
+		
+	assert_submodule_url("TestGitRepository", git_repository_workdir(g_repo));
+}
+
+static void assert_submodule_url(const char* name, const char *url)
+{
+	git_config *cfg;
+	const char *s;
+	git_buf key = GIT_BUF_INIT;
+
+	cl_git_pass(git_repository_config(&cfg, g_repo));
+
+	cl_git_pass(git_buf_printf(&key, "submodule.%s.url", name));
+	cl_git_pass(git_config_get_string(&s, cfg, git_buf_cstr(&key)));
+	cl_assert_equal_s(s, url);
+
+	git_config_free(cfg);
+	git_buf_free(&key);
+}
diff --git a/tests/submodule/modify.c b/tests/submodule/modify.c
index 7cd44e2..7e76f35 100644
--- a/tests/submodule/modify.c
+++ b/tests/submodule/modify.c
@@ -7,85 +7,12 @@ static git_repository *g_repo = NULL;
 
 #define SM_LIBGIT2_URL "https://github.com/libgit2/libgit2.git"
 #define SM_LIBGIT2     "sm_libgit2"
-#define SM_LIBGIT2B    "sm_libgit2b"
-
-#define SM_RELATIVE_URL "../TestGitRepository"
-#define SM_RELATIVE_RESOLVED_URL "https://github.com/libgit2/TestGitRepository"
-#define SM_RELATIVE "TestGitRepository"
 
 void test_submodule_modify__initialize(void)
 {
 	g_repo = setup_fixture_submod2();
 }
 
-void test_submodule_modify__add(void)
-{
-	git_submodule *sm;
-	git_config *cfg;
-	const char *s;
-
-	/* re-add existing submodule */
-	cl_assert_equal_i(
-		GIT_EEXISTS,
-		git_submodule_add_setup(NULL, g_repo, "whatever", "sm_unchanged", 1));
-
-	/* add a submodule using a gitlink */
-
-	cl_git_pass(
-		git_submodule_add_setup(&sm, g_repo, SM_LIBGIT2_URL, SM_LIBGIT2, 1)
-		);
-	git_submodule_free(sm);
-
-	cl_assert(git_path_isfile("submod2/" SM_LIBGIT2 "/.git"));
-
-	cl_assert(git_path_isdir("submod2/.git/modules"));
-	cl_assert(git_path_isdir("submod2/.git/modules/" SM_LIBGIT2));
-	cl_assert(git_path_isfile("submod2/.git/modules/" SM_LIBGIT2 "/HEAD"));
-
-	cl_git_pass(git_repository_config(&cfg, g_repo));
-	cl_git_pass(
-		git_config_get_string(&s, cfg, "submodule." SM_LIBGIT2 ".url"));
-	cl_assert_equal_s(s, SM_LIBGIT2_URL);
-	git_config_free(cfg);
-
-	/* add a submodule not using a gitlink */
-
-	cl_git_pass(
-		git_submodule_add_setup(&sm, g_repo, SM_LIBGIT2_URL, SM_LIBGIT2B, 0)
-		);
-	git_submodule_free(sm);
-
-	cl_assert(git_path_isdir("submod2/" SM_LIBGIT2B "/.git"));
-	cl_assert(git_path_isfile("submod2/" SM_LIBGIT2B "/.git/HEAD"));
-	cl_assert(!git_path_exists("submod2/.git/modules/" SM_LIBGIT2B));
-
-	cl_git_pass(git_repository_config(&cfg, g_repo));
-	cl_git_pass(
-		git_config_get_string(&s, cfg, "submodule." SM_LIBGIT2B ".url"));
-	cl_assert_equal_s(s, SM_LIBGIT2_URL);
-	git_config_free(cfg);
-}
-
-void test_submodule_modify__add_with_relative_url(void) {
-	git_submodule *sm;
-	git_config *cfg;
-	const char *s;
-
-	git_repository* repo;
-	/* setup_fixture_submod2 does not work here because it does not set up origin configuration */
-	cl_git_pass(git_clone(&repo, SM_LIBGIT2_URL, "./sandbox/submodules_cloned", NULL));
-
-	cl_git_pass(
-		git_submodule_add_setup(&sm, repo, SM_RELATIVE_URL, SM_RELATIVE, 1)
-		);
-
-	cl_git_pass(git_repository_config(&cfg, repo));
-	cl_git_pass(
-		git_config_get_string(&s, cfg, "submodule." SM_RELATIVE ".url"));
-	cl_assert_equal_s(s, SM_RELATIVE_RESOLVED_URL);
-	git_config_free(cfg);
-}
-
 static int delete_one_config(const git_config_entry *entry, void *payload)
 {
 	git_config *cfg = payload;