After doing the operation:
$ fossil mv filea fileb
$ mv filea fileb

A status shows a rename for 'fileb'. Trying to run:
$ fossil commit fileb

shows:
fossil: file 'fileb' has not changed

So having other changes in the working directory, I don't know how could I commit only the rename.

but

fossil commit

will work.

Yes, "fossil commit" will work, but partial commit as in "fossil commit file1 file2" will not work.

I have the same problem even with the most recent version of fossil [cf178577ec].

The only way I can commit a rename/mv is by committing all the files which is not what I want to do.  I have stuff pending that is not ready to be committed but the rename can be committed now.