Use .tmp before the file extension (#529)

When creating temporary files use the pattern `.tmp.ext` instead of
`.ext.tmp` to be consistent with Factorio which creates `.tmp.zip` files
during saving.

If patching fails this will leave a `.tmp.zip` file in the instance saves
directory which is ignored by the default save selector.

Resolves #486.

packages/host/src/patch.ts

@@ -417,7 +417,7 @@ export async function patch(savePath: string, modules: SaveModule[]) {
 	root.file("clusterio.json", JSON.stringify(patchInfo, null, "\t"));
 
 	// Write back the save
-	let tempSavePath = `${savePath}.tmp`;
+	let tempSavePath = savePath.replace(/(\.zip)?$/, ".tmp.zip");
 	let stream = zip.generateNodeStream({ compression: "DEFLATE" });
 	let fd = await fs.open(tempSavePath, "w");
 	try {