Remote paths: canonicalize UNC paths on Win32

Git for Windows will handle UNC paths only when in forward-slash
format, eg "//server/path".  When given a UNC path as a remote,
rewrite standard format ("\\server\path") into this ridiculous
format.

src/remote.c

@@ -114,10 +114,30 @@ static int get_check_cert(int *out, git_repository *repo)
 }
 #endif
 
+static int canonicalize_url(git_buf *out, const char *in)
+{
+	const char *c;
+
+#ifdef GIT_WIN32
+	/* Given a UNC path like \\server\path, we need to convert this
+	 * to //server/path for compatibility with core git.
+	 */
+	if (in[0] == '\\' && in[1] == '\\' &&
+		(git__isalpha(in[2]) || git__isdigit(in[2]))) {
+		for (c = in; *c; c++)
+			git_buf_putc(out, *c == '\\' ? '/' : *c);
+
+		return git_buf_oom(out) ? -1 : 0;
+	}
+#endif
+
+	return git_buf_puts(out, in);
+}
+
 static int create_internal(git_remote **out, git_repository *repo, const char *name, const char *url, const char *fetch)
 {
 	git_remote *remote;
-	git_buf fetchbuf = GIT_BUF_INIT;
+	git_buf canonical_url = GIT_BUF_INIT, fetchbuf = GIT_BUF_INIT;
 	int error = -1;
 
 	/* name is optional */
@@ -129,11 +149,11 @@ static int create_internal(git_remote **out, git_repository *repo, const char *n
 	remote->repo = repo;
 	remote->update_fetchhead = 1;
 
-	if (git_vector_init(&remote->refs, 32, NULL) < 0)
+	if (git_vector_init(&remote->refs, 32, NULL) < 0 ||
+		canonicalize_url(&canonical_url, url) < 0)
 		goto on_error;
 
-	remote->url = git__strdup(url);
-	GITERR_CHECK_ALLOC(remote->url);
+	remote->url = git_buf_detach(&canonical_url);
 
 	if (name != NULL) {
 		remote->name = git__strdup(name);
@@ -151,11 +171,13 @@ static int create_internal(git_remote **out, git_repository *repo, const char *n
 
 	*out = remote;
 	git_buf_free(&fetchbuf);
+	git_buf_free(&canonical_url);
 	return 0;
 
 on_error:
 	git_remote_free(remote);
 	git_buf_free(&fetchbuf);
+	git_buf_free(&canonical_url);
 	return error;
 }
 

tests/clone/local.c

@@ -16,6 +16,40 @@ static int file_url(git_buf *buf, const char *host, const char *path)
 	return git_buf_printf(buf, "file://%s/%s", host, path);
 }
 
+static int git_style_unc_path(git_buf *buf, const char *host, const char *path)
+{
+	git_buf_clear(buf);
+
+	if (host)
+		git_buf_printf(buf, "//%s/", host);
+
+	if (path[0] == '/')
+		path++;
+
+	if (isalpha(path[0]) && path[1] == ':' && path[2] == '/') {
+		git_buf_printf(buf, "%c$/", path[0]);
+		path += 3;
+	}
+
+	git_buf_puts(buf, path);
+
+	return git_buf_oom(buf) ? -1 : 0;
+}
+
+static int unc_path(git_buf *buf, const char *host, const char *path)
+{
+	char *c;
+
+	if (git_style_unc_path(buf, host, path) < 0)
+		return -1;
+
+	for (c = buf->ptr; *c; c++)
+		if (*c == '/')
+			*c = '\\';
+
+	return 0;
+}
+
 void test_clone_local__should_clone_local(void)
 {
 	git_buf buf = GIT_BUF_INIT;
@@ -121,3 +155,57 @@ void test_clone_local__hardlinks(void)
 	cl_git_pass(git_futils_rmdir_r("./clone3.git", NULL, GIT_RMDIR_REMOVE_FILES));
 	cl_git_pass(git_futils_rmdir_r("./clone4.git", NULL, GIT_RMDIR_REMOVE_FILES));
 }
+
+void test_clone_local__standard_unc_paths_are_written_git_style(void)
+{
+#ifdef GIT_WIN32
+	git_repository *repo;
+	git_remote *remote;
+	git_clone_options opts = GIT_CLONE_OPTIONS_INIT;
+	git_buf unc = GIT_BUF_INIT, git_unc = GIT_BUF_INIT;
+
+	/* we use a fixture path because it needs to exist for us to want to clone */
+	const char *path = cl_fixture("testrepo.git");
+
+	cl_git_pass(unc_path(&unc, "localhost", path));
+	cl_git_pass(git_style_unc_path(&git_unc, "localhost", path));
+
+	cl_git_pass(git_clone(&repo, unc.ptr, "./clone.git", &opts));
+	cl_git_pass(git_remote_load(&remote, repo, "origin"));
+
+	cl_assert_equal_s(git_unc.ptr, git_remote_url(remote));
+
+	git_remote_free(remote);
+	git_repository_free(repo);
+	git_buf_free(&unc);
+	git_buf_free(&git_unc);
+
+	cl_git_pass(git_futils_rmdir_r("./clone.git", NULL, GIT_RMDIR_REMOVE_FILES));
+#endif
+}
+
+void test_clone_local__git_style_unc_paths(void)
+{
+#ifdef GIT_WIN32
+	git_repository *repo;
+	git_remote *remote;
+	git_clone_options opts = GIT_CLONE_OPTIONS_INIT;
+	git_buf git_unc = GIT_BUF_INIT;
+
+	/* we use a fixture path because it needs to exist for us to want to clone */
+	const char *path = cl_fixture("testrepo.git");
+
+	cl_git_pass(git_style_unc_path(&git_unc, "localhost", path));
+
+	cl_git_pass(git_clone(&repo, git_unc.ptr, "./clone.git", &opts));
+	cl_git_pass(git_remote_load(&remote, repo, "origin"));
+
+	cl_assert_equal_s(git_unc.ptr, git_remote_url(remote));
+
+	git_remote_free(remote);
+	git_repository_free(repo);
+	git_buf_free(&git_unc);
+
+	cl_git_pass(git_futils_rmdir_r("./clone.git", NULL, GIT_RMDIR_REMOVE_FILES));
+#endif
+}