Combined -odir/-hidir flag
Many of my command line invocations are:
ghc -odir obj -hidir obj ...
I nearly always set both
-hidir to the same thing, typically to just ask for the temporary files to not crowd the code files. It would be useful if there was one combined flag, perhaps
-tdir (temporary), which gave default values to both
Another option (suggested by quicksilver) is that
-hidir could default to
-odir unless set explicitly - since .hi files are really just compiler details, as far as the user is concerned.