testing: generate tests operations using Hypothesis
The idea of this patch is to expand the use of Hypothesis
within Mercurial to use its concept of "stateful testing".
The result is a test which runs a sequence of operations
against a Mercurial repository. Each operation is given a
set of allowed ways it can fail. Any other non-zero exit
code is a test failure.
At the end, the whole sequence is then reverified by
generating a .t test and testing it again in pure
mode (this is also useful for catching non-determinism
bugs).
This has proven reasonably effective at finding bugs,
and has identified two problems in the shelve extension
already (
issue5113 and
issue5112).