After the most recent update of SourceTree (1.7.0.1) I am noticing that adding files to the index and then clicking Commit and the box that says "Amend latest commit", this will no longer fill in the original commit message. Instead, an error message gets printed in the commit message box:

fatal: ambiguous argument 'HEAD': both revision and filename
Use '--' to separate filenames from revisions

If I just blindly continue and do the amend (as I used to do), this will be used as the commit message, and the original message will be lost.

I believe this is new behavior to version 1.7.0.1.