Xcode: changing double clicking file behavior

Question

One of my projects suddenly had its double-clicking behavior changed and I don't know how to change it back.

The behavior I want:

Double clicking a source code file opens up a new window.

The behavior I have:

Double clicking a source code file opens the file in the existing window. This results in only allowing one window open for the project at any time.

Needless to say this is a bit frustrating. I can't find any preference that seems to control this. It seems to be a per-project preference (it is only happening in one project). Any ideas?

Note: I am using the condensed layout.

Note 2: "Open in Separate Editor" does not work.

Answer 1

In XCode 6, click "Preferences...", then "Navigation", then under "Double Click Navigation" select "Same as Click"