Make it an error to make an alias that matches a tag name.
Make it an error to make an alias that matches a tag name.

(This was just a bug, of course it was never supposed to be allowed.)

If you have such aliases your log parsing will now fail. The previous
commit will then come in handy to let you find the offending lines (and
remove them).

drougge/wellpapp,drougge/wellpapp,drougge/wellpapp