Allow items to provide savePanel options.

src/atom.coffee

@@ -783,11 +783,12 @@ class Atom extends Model
   showSaveDialog: (callback) ->
     callback(showSaveDialogSync())
 
-  showSaveDialogSync: (defaultPath) ->
-    defaultPath ?= @project?.getPaths()[0]
+  showSaveDialogSync: (options={}) ->
     currentWindow = @getCurrentWindow()
     dialog = remote.require('dialog')
-    dialog.showSaveDialog currentWindow, {title: 'Save File', defaultPath}
+    options.title ?= 'Save File'
+    options.defaultPath ?= @project?.getPaths()[0]
+    dialog.showSaveDialog currentWindow, options
 
   saveSync: ->
     if storageKey = @constructor.getStateKey(@project?.getPaths(), @mode)

src/pane.coffee

@@ -492,8 +492,9 @@ class Pane extends Model
   saveItemAs: (item, nextAction) ->
     return unless item?.saveAs?
 
-    itemPath = item.getPath?()
-    newItemPath = atom.showSaveDialogSync(itemPath)
+    saveOptions = item.getSaveOptions?() or {}
+    saveOptions.defaultPath ?= item.getPath()
+    newItemPath = atom.showSaveDialogSync(saveOptions)
     if newItemPath
       try
         item.saveAs(newItemPath)