diffutils proposal: cmp FILE DIR/ ==> cmp FILE DIR/$(basename FILE)

[Chris Chittleborough]

I think cmp would be more expert-friendly if it acted like diff when 
asked to compare a file to a directory -- that is, it should look for a 
file in the specified directory with the same basename as the specified 
file.
More formally, using bash for notation, I want
      cmp FILE DIR/     ==>  cmp FILE DIR/$(basename FILE)
  and cmp DIR/  FILE    ==>  cmp DIR/$(basename FILE) FILE

(The Single Unix Specification allows read(2) from a directory to fail
with EISDIR. GNU/Linux does this. On such systems, cmp FILE DIR 
currently fails with "cmp: DIR: Is a directory".)

It is easy to patch cmp.c to do this in either of two ways:
  (1) If one filename arg ends with '/' and the other does not (and
      is not "-"), append the basename of the latter to the former.
  (2) Once we have opened and fstat()ed the two files, see if one is
      a directory and the other a file with a non-"-" name; if so,
      close the directory and try to open the appropriate file in
      that directory.

The reason I'm posting this is to ask:
  * Which of these two approaches do people think is better?
  * Would the diffutils maintainers like a patch that makes this
    change (and updates the documentation)?

(BTW, my next project is to add --from-related-file=PATTERN to diff.)
Does anyone have any comments about this