thodg/libgit2

diff --git a/src/config.c b/src/config.c
index 1a205fe..b3168f7 100644
--- a/src/config.c
+++ b/src/config.c
@@ -615,6 +615,36 @@ int git_config_set_string(git_config *cfg, const char *name, const char *value)
 	return error;
 }
 
+int git_config__update_entry(
+	git_config *config,
+	const char *key,
+	const char *value,
+	bool overwrite_existing,
+	bool only_if_existing)
+{
+	int error = 0;
+	const git_config_entry *ce = NULL;
+
+	if ((error = git_config__lookup_entry(&ce, config, key, false)) < 0)
+		return error;
+
+	if (!ce && only_if_existing) /* entry doesn't exist */
+		return 0;
+	if (ce && !overwrite_existing) /* entry would be overwritten */
+		return 0;
+	if (value && ce && ce->value && !strcmp(ce->value, value)) /* no change */
+		return 0;
+	if (!value && (!ce || !ce->value)) /* asked to delete absent entry */
+		return 0;
+
+	if (!value)
+		error = git_config_delete_entry(config, key);
+	else
+		error = git_config_set_string(config, key, value);
+
+	return error;
+}
+
 /***********
  * Getters
  ***********/
diff --git a/src/config.h b/src/config.h
index 03d9106..00b6063 100644
--- a/src/config.h
+++ b/src/config.h
@@ -53,6 +53,14 @@ extern int git_config__lookup_entry(
 	const char *key,
 	bool no_errors);
 
+/* internal only: update and/or delete entry string with constraints */
+extern int git_config__update_entry(
+	git_config *cfg,
+	const char *key,
+	const char *value,
+	bool overwrite_existing,
+	bool only_if_existing);
+
 /*
  * Lookup functions that cannot fail.  These functions look up a config
  * value and return a fallback value if the value is missing or if any
diff --git a/src/remote.c b/src/remote.c
index 62ee903..53ff797 100644
--- a/src/remote.c
+++ b/src/remote.c
@@ -495,9 +495,10 @@ cleanup:
 int git_remote_save(const git_remote *remote)
 {
 	int error;
-	git_config *config;
+	git_config *cfg;
 	const char *tagopt = NULL;
 	git_buf buf = GIT_BUF_INIT;
+	const git_config_entry *existing;
 
 	assert(remote);
 
@@ -509,43 +510,31 @@ int git_remote_save(const git_remote *remote)
 	if ((error = ensure_remote_name_is_valid(remote->name)) < 0)
 		return error;
 
-	if (git_repository_config__weakptr(&config, remote->repo) < 0)
-		return -1;
+	if ((error = git_repository_config__weakptr(&cfg, remote->repo)) < 0)
+		return error;
 
-	if (git_buf_printf(&buf, "remote.%s.url", remote->name) < 0)
-		return -1;
+	if ((error = git_buf_printf(&buf, "remote.%s.url", remote->name)) < 0)
+		return error;
 
-	if (git_config_set_string(config, git_buf_cstr(&buf), remote->url) < 0) {
-		git_buf_free(&buf);
-		return -1;
-	}
+	/* after this point, buffer is allocated so end with cleanup */
+
+	if ((error = git_config_set_string(
+			cfg, git_buf_cstr(&buf), remote->url)) < 0)
+		goto cleanup;
 
 	git_buf_clear(&buf);
-	if (git_buf_printf(&buf, "remote.%s.pushurl", remote->name) < 0)
-		return -1;
+	if ((error = git_buf_printf(&buf, "remote.%s.pushurl", remote->name)) < 0)
+		goto cleanup;
 
-	if (remote->pushurl) {
-		if (git_config_set_string(config, git_buf_cstr(&buf), remote->pushurl) < 0) {
-			git_buf_free(&buf);
-			return -1;
-		}
-	} else {
-		int error = git_config_delete_entry(config, git_buf_cstr(&buf));
-		if (error == GIT_ENOTFOUND) {
-			error = 0;
-			giterr_clear();
-		}
-		if (error < 0) {
-			git_buf_free(&buf);
-			return error;
-		}
-	}
+	if ((error = git_config__update_entry(
+			cfg, git_buf_cstr(&buf), remote->pushurl, true, false)) < 0)
+		goto cleanup;
 
-	if (update_config_refspec(remote, config, GIT_DIRECTION_FETCH) < 0)
-		goto on_error;
+	if ((error = update_config_refspec(remote, cfg, GIT_DIRECTION_FETCH)) < 0)
+		goto cleanup;
 
-	if (update_config_refspec(remote, config, GIT_DIRECTION_PUSH) < 0)
-		goto on_error;
+	if ((error = update_config_refspec(remote, cfg, GIT_DIRECTION_PUSH)) < 0)
+		goto cleanup;
 
 	/*
 	 * What action to take depends on the old and new values. This
@@ -561,31 +550,26 @@ int git_remote_save(const git_remote *remote)
 	 */
 
 	git_buf_clear(&buf);
-	if (git_buf_printf(&buf, "remote.%s.tagopt", remote->name) < 0)
-		goto on_error;
-
-	error = git_config_get_string(&tagopt, config, git_buf_cstr(&buf));
-	if (error < 0 && error != GIT_ENOTFOUND)
-		goto on_error;
+	if ((error = git_buf_printf(&buf, "remote.%s.tagopt", remote->name)) < 0)
+		goto cleanup;
 
-	if (remote->download_tags == GIT_REMOTE_DOWNLOAD_TAGS_ALL) {
-		if (git_config_set_string(config, git_buf_cstr(&buf), "--tags") < 0)
-			goto on_error;
-	} else if (remote->download_tags == GIT_REMOTE_DOWNLOAD_TAGS_NONE) {
-		if (git_config_set_string(config, git_buf_cstr(&buf), "--no-tags") < 0)
-			goto on_error;
-	} else if (tagopt) {
-		if (git_config_delete_entry(config, git_buf_cstr(&buf)) < 0)
-			goto on_error;
-	}
+	if ((error = git_config__lookup_entry(
+			&existing, cfg, git_buf_cstr(&buf), false)) < 0)
+		goto cleanup;
 
-	git_buf_free(&buf);
+	if (remote->download_tags == GIT_REMOTE_DOWNLOAD_TAGS_ALL)
+		tagopt = "--tags";
+	else if (remote->download_tags == GIT_REMOTE_DOWNLOAD_TAGS_NONE)
+		tagopt = "--no-tags";
+	else if (existing != NULL)
+		tagopt = NULL;
 
-	return 0;
+	error = git_config__update_entry(
+		cfg, git_buf_cstr(&buf), tagopt, true, false);
 
-on_error:
+cleanup:
 	git_buf_free(&buf);
-	return -1;
+	return error;
 }
 
 const char *git_remote_name(const git_remote *remote)
diff --git a/src/submodule.c b/src/submodule.c
index a0ce531..dc0ea43 100644
--- a/src/submodule.c
+++ b/src/submodule.c
@@ -83,7 +83,6 @@ static int lookup_head_remote(git_buf *url, git_repository *repo);
 static int submodule_get(git_submodule **, git_repository *, const char *, const char *);
 static int submodule_load_from_config(const git_config_entry *, void *);
 static int submodule_load_from_wd_lite(git_submodule *);
-static int submodule_update_config(git_submodule *, const char *, const char *, bool, bool);
 static void submodule_get_index_status(unsigned int *, git_submodule *);
 static void submodule_get_wd_status(unsigned int *, git_submodule *, git_repository *, git_submodule_ignore_t);
 
@@ -716,46 +715,105 @@ git_submodule_recurse_t git_submodule_set_fetch_recurse_submodules(
 	return old;
 }
 
-int git_submodule_init(git_submodule *submodule, int overwrite)
+int git_submodule_init(git_submodule *sm, int overwrite)
 {
 	int error;
 	const char *val;
+	git_buf key = GIT_BUF_INIT;
+	git_config *cfg = NULL;
 
-	/* write "submodule.NAME.url" */
-
-	if (!submodule->url) {
+	if (!sm->url) {
 		giterr_set(GITERR_SUBMODULE,
-			"No URL configured for submodule '%s'", submodule->name);
+			"No URL configured for submodule '%s'", sm->name);
 		return -1;
 	}
 
-	error = submodule_update_config(
-		submodule, "url", submodule->url, overwrite != 0, false);
-	if (error < 0)
+	if ((error = git_repository_config(&cfg, sm->repo)) < 0)
 		return error;
 
+	/* write "submodule.NAME.url" */
+
+	if ((error = git_buf_printf(&key, "submodule.%s.url", sm->name)) < 0 ||
+		(error = git_config__update_entry(
+			cfg, key.ptr, sm->url, overwrite != 0, false)) < 0)
+		goto cleanup;
+
 	/* write "submodule.NAME.update" if not default */
 
-	val = (submodule->update == GIT_SUBMODULE_UPDATE_CHECKOUT) ?
-		NULL : git_submodule_update_to_str(submodule->update);
-	error = submodule_update_config(
-		submodule, "update", val, (overwrite != 0), false);
+	val = (sm->update == GIT_SUBMODULE_UPDATE_CHECKOUT) ?
+		NULL : git_submodule_update_to_str(sm->update);
+
+	if ((error = git_buf_printf(&key, "submodule.%s.update", sm->name)) < 0 ||
+		(error = git_config__update_entry(
+			cfg, key.ptr, val, overwrite != 0, false)) < 0)
+		goto cleanup;
+
+	/* success */
+
+cleanup:
+	git_config_free(cfg);
+	git_buf_free(&key);
 
 	return error;
 }
 
-int git_submodule_sync(git_submodule *submodule)
+int git_submodule_sync(git_submodule *sm)
 {
-	if (!submodule->url) {
+	int error = 0;
+	git_config *cfg = NULL;
+	git_buf key = GIT_BUF_INIT;
+
+	if (!sm->url) {
 		giterr_set(GITERR_SUBMODULE,
-			"No URL configured for submodule '%s'", submodule->name);
+			"No URL configured for submodule '%s'", sm->name);
 		return -1;
 	}
 
 	/* copy URL over to config only if it already exists */
 
-	return submodule_update_config(
-		submodule, "url", submodule->url, true, true);
+	if (!(error = git_repository_config__weakptr(&cfg, sm->repo)) &&
+		!(error = git_buf_printf(&key, "submodule.%s.url", sm->name)))
+		error = git_config__update_entry(cfg, key.ptr, sm->url, true, true);
+
+	/* if submodule exists in the working directory, update remote url */
+
+	if (!error && (sm->flags & GIT_SUBMODULE_STATUS_IN_WD) != 0) {
+		git_repository *smrepo = NULL;
+		git_reference *smhead = NULL;
+		const char *remote = "origin";
+
+		if ((error = git_submodule_open(&smrepo, sm)) < 0 ||
+			(error = git_repository_head(&smhead, smrepo)) < 0 ||
+			(error = git_repository_config__weakptr(&cfg, smrepo)) < 0)
+			goto smcleanup;
+
+		/* get remote for default branch and set remote.<name>.url */
+
+		if (git_reference_type(smhead) == GIT_REF_SYMBOLIC) {
+			const char *bname = git_reference_shorthand(smhead);
+			const git_config_entry *ce;
+
+			git_buf_clear(&key);
+			if ((error = git_buf_printf(&key, "branch.%s.remote", bname)) < 0 ||
+				(error = git_config__lookup_entry(&ce, cfg, key.ptr, 0)) < 0)
+				goto smcleanup;
+
+			if (ce && ce->value)
+				remote = ce->value;
+		}
+
+		git_buf_clear(&key);
+		if (!(error = git_buf_printf(&key, "remote.%s.url", remote)))
+			error = git_config__update_entry(cfg, key.ptr, sm->url, true, true);
+
+smcleanup:
+		git_reference_free(smhead);
+		git_repository_free(smrepo);
+	}
+
+	git_buf_free(&key);
+
+	return error;
 }
 
 static int git_submodule__open(
@@ -1640,50 +1698,6 @@ cleanup:
 	return error;
 }
 
-static int submodule_update_config(
-	git_submodule *submodule,
-	const char *attr,
-	const char *value,
-	bool overwrite,
-	bool only_existing)
-{
-	int error;
-	git_config *config;
-	git_buf key = GIT_BUF_INIT;
-	const git_config_entry *ce = NULL;
-
-	assert(submodule);
-
-	error = git_repository_config__weakptr(&config, submodule->repo);
-	if (error < 0)
-		return error;
-
-	error = git_buf_printf(&key, "submodule.%s.%s", submodule->name, attr);
-	if (error < 0)
-		goto cleanup;
-
-	if ((error = git_config__lookup_entry(&ce, config, key.ptr, false)) < 0)
-		goto cleanup;
-
-	if (!ce && only_existing)
-		goto cleanup;
-	if (ce && !overwrite)
-		goto cleanup;
-	if (value && ce && ce->value && !strcmp(ce->value, value))
-		goto cleanup;
-	if (!value && (!ce || !ce->value))
-		goto cleanup;
-
-	if (!value)
-		error = git_config_delete_entry(config, key.ptr);
-	else
-		error = git_config_set_string(config, key.ptr, value);
-
-cleanup:
-	git_buf_free(&key);
-	return error;
-}
-
 static void submodule_get_index_status(unsigned int *status, git_submodule *sm)
 {
 	const git_oid *head_oid  = git_submodule_head_id(sm);