I'm afraid it's not that simple. The patch will cause diff3 to output
that warning, since diff3 uses diff without --normal, so diff3.c needs
fixing. Also, the manual needs fixing (doc/diffutils.texi). And the
output of "diff --help" (src/diff.c). And there should be a test case
testing the new behavior.
More important. Suppose I want a program with GNU diff's traditional
behavior and so use a shell script 'mydiff' like this:
#!/bin/sh
exec diff --normal "$@"
This won't work, because if I invoke the script like this:
mydiff -c foo bar
diff will complain about --normal conflicting with -c. So I suppose diff
needs to change so that later output specifiers override earlier. But
here things are a bit tricky, e.g., right now '-C5 -c' is equivalent to
'-c -C5' and I assume we don't want to change this.
One other idea. If the invoker uses any long option, or any option other
than -b and -r, diff can default to the -u output format regardless of
whether POSIXLY_CORRECT is set. This is because POSIX does not specify
the behavior of these other options.
Plus, it would be nice if we could address Eric's concerns somehow.
I hope I haven't scared you away entirely....
