sparse: clean up config signature code Before, 0 was being used as the default signature value and we cast the int to a string. We also handled I/O exceptions manually. The new code uses cfs.tryread() so we always feed data into the hasher. The empty string does hash and and should be suitable for input into a cache key. The changes made the code simple enough that the separate checksum function could be inlined.

sparse: move config signature logic into core This is a pretty straightforward port. It will be cleaned up in a subsequent commit.

sparse: remove custom hash matcher With the recent change to always use repr(), this function was functionally identical to the version in fsmonitor it was replacing. So remove it.

sparse: override __repr__ in matchers sparse.py in FB's hg-experimental repo switched to using __repr__ for non-sparse matchers soon after hg core started overriding __repr__ in the matchers in match.py (because the core matchers also stopped having "includepat" and other attributes that sparse used to depend on). Let's finish that migration by implementing __repr__ in the sparse matchers as well. That also lets us remove the special handling of them in _hashmatcher().

tests: fix reference to undefined variable The delaypush() function had a reference to "repo" that was clearly supposed to be "pushop.repo". Instead of just fixing that, let's extract "pushop.repo.ui" to a variable, since that's the only piece of the repo that's needed in the function. I have not looked into why I saw a different result in the test to start with, but that's for another patch anyway.

shelve: don't reimplement mergestate.unresolved()

summary: don't reimplment mergestate.unresolved()