People keep having trouble with the ! syntax for negation, because of
the !-history feature in some shells (notably, enabled by default in
bash in all distros).

The result is that attempts to deallocate hosts, or do some other
things, produces an incomprensible "event not found" message.

I don't suffer from this because I have it turned off, with set -H.
IMO it should be off by default.  (This is Debian #897422.)

Avoid this whole problem by using ^ everywhere we previously used !
for negation.  (We continue to honour !.)

Places where ! is still the necessary syntactic character to do
something in osstest are:

 * In the ms-queuedaemon protocol, ! is used to indicate an
   unsolicited response.

 * In sg-run-job, ! in an IFFAIL means to run a step even if
   the job has failed or is being truncated.

These go nowhere near a shell and are not, conceptually, negation.


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