Move unrelated code out of menu.js and ipc.js

main/shell.js

@@ -0,0 +1,32 @@
+module.exports = {
+  openExternal,
+  openItem,
+  showItemInFolder
+}
+
+var electron = require('electron')
+var log = require('./log')
+
+/**
+ * Open the given external protocol URL in the desktop’s default manner.
+ */
+function openExternal (url) {
+  log(`openExternal: ${url}`)
+  electron.shell.openExternal(url)
+}
+
+/**
+ * Open the given file in the desktop’s default manner.
+ */
+function openItem (path) {
+  log(`openItem: ${path}`)
+  electron.shell.openItem(path)
+}
+
+/**
+ * Show the given file in a file manager. If possible, select the file.
+ */
+function showItemInFolder (path) {
+  log(`showItemInFolder: ${path}`)
+  electron.shell.showItemInFolder(path)
+}