Adding redo-whichdo wasn't so hard, except that it exposed a bunch of
mistakes in the way minimal/do was choosing .do files. Most of the
wrong names it tried didn't matter (since they're very unlikely to
exist) except that they produce the wrong redo-whichdo output.
Debugging that took so much effort that I added unit tests for some
functions to make it easier to find problems in the future.
Note: this change apparently makes minimal/do about 50% slower than
before, because the _find_dofiles algorithm got less optimized (but
more readable). It's still not very slow, and anyway, since it's
minimal/do, I figured readable/correct code probably outweighed a bit
of speed. (Although if anyone can come up with an algorithm that's
clear *and* works better, I won't turn it down :) I feel like I must
be doing it the hard way...)
This includes a fairly detailed test of various known shell bugs from the
autoconf docs.
The idea here is that if redo works on your system, you should be able to
rely on a *good* shell to run your .do files; you shouldn't have to work
around zillions of bugs like autoconf does.
