Validate proxy URL on Windows.

src/libgit2/transports/http.c

@@ -334,16 +334,13 @@ static int lookup_proxy(
 		return 0;
 	}
 
-	if (!proxy)
-		goto done;
-
-
-	if ((error = git_net_url_parse(&transport->proxy.url, proxy) < 0))
+	if (!proxy ||
+	    (error = git_net_url_parse(&transport->proxy.url, proxy)) < 0)
 		goto done;
 
 	if (!git_net_url_valid(&transport->proxy.url)) {
-		git_error_set(GIT_ERROR_HTTP, "invalid proxy url: %s", proxy);
-		error = GIT_EINVALIDSPEC;
+		git_error_set(GIT_ERROR_HTTP, "invalid URL: '%s'", proxy);
+		error = -1;
 		goto done;
 	}
 

src/libgit2/transports/winhttp.c

@@ -446,7 +446,7 @@ static int winhttp_stream_connect(winhttp_stream *s)
 		if ((error = git_net_url_parse(&t->proxy.url, proxy_url)) < 0)
 			goto on_error;
 
-		if (strcmp(t->proxy.url.scheme, "http") != 0 && strcmp(t->proxy.url.scheme, "https") != 0) {
+		if (!git_net_url_valid(&t->proxy.url)) {
 			git_error_set(GIT_ERROR_HTTP, "invalid URL: '%s'", proxy_url);
 			error = -1;
 			goto on_error;

tests/libgit2/online/clone.c

@@ -975,10 +975,10 @@ void test_online_clone__proxy_invalid_url(void)
 	g_options.fetch_opts.proxy_opts.certificate_check = proxy_cert_cb;
 
 	g_options.fetch_opts.proxy_opts.url = "noschemeorport";
-	cl_git_fail_with(GIT_EINVALIDSPEC, git_clone(&g_repo, "http://github.com/libgit2/TestGitRepository", "./foo", &g_options));
+	cl_git_fail(git_clone(&g_repo, "http://github.com/libgit2/TestGitRepository", "./foo", &g_options));
 
 	g_options.fetch_opts.proxy_opts.url = "noscheme:8080";
-	cl_git_fail_with(GIT_EINVALIDSPEC, git_clone(&g_repo, "http://github.com/libgit2/TestGitRepository", "./foo", &g_options));
+	cl_git_fail(git_clone(&g_repo, "http://github.com/libgit2/TestGitRepository", "./foo", &g_options));
 }
 
 void test_online_clone__proxy_credentials_request(void)