Doing diffs between branches post-commit

[James Bloom Scheff]

I'm trying to look at code changes that were made in a bitbucket branch. I keep getting "there are no changes to display". I'm new to bitbucket, but the people here who are familiar with bitbucket tell me that one can't look at changes made in a branch after is has been committed. I know that that can't be correct. So my question is, how do I look at the changes made in a branch post-commit.