Given a changeset filename, you can use this goodie to check an older .cs/.st file for conflicts with methods from more recent update-changesets in your image. Its output is displayed in a Transcript window.
Example usage: 'FilePackage conflictsWithUpdatedMethods: 'MyChangeSet.cs'.' Or, use the 'conflicts with updated methods' menu item or 'conflicts' button in the FileList window.
The ConflictChecker doesn't just check to see which methods in a changeset would overwrite methods in the image... it actually checks to see if there have been more recent updates to the image since the changeset was created*, in which case the more recent methods would be overwritten by older methods from your changeset if you filed it in, which would likely break things. It's basically a 3-way conflict check.
*It uses the latest update # from the .cs/.st file header as a basis for comparison.
Generally, you should use a reasonably fresh image to do this, and the image should have update-changesets going as far back as possible (at least as far back as the changeset you want to test).