"Sort Lines in Selection" for Xcode 4

You can do this with Automator:

• Start Automator and select either:
  "Service" for macOS 10.7 or
  "New Document" followed by "Quick Action" for macOS 11
• Find and drag "Run Shell Script" into the workflow panel
• Select "Output replaces selected text"
• Type sort -f into the "Run Shell Script" textfield
• Save

Now you can sort lines in any textfield. Select some text and right-click or Control click and select the service you just created.

After 4 years Xcode still doesn't have this feature builtin, but now it supports extensions. So here you go: "xcsort" is an extension to sort text in Xcode 8. It adds a command to sort lines in selection.