annotate COPYING @ 51332:2e169a222e63

delta-find: fix the computation of the `prev` value

The previous computation was "wrong" it always used the tiprev, even when computing a delta in a non-append case (mostly benchmark).

This never produced wrong delta on disk, but would misled debug or performance command. Since it does not have any actual user impact, I did not put this on stable.

With the code fixed we can now use revisions in some search and it makes the
test display more interesting behavior since the algorithm has more to work
with.

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