rust-index: moved constructor in separate impl block with the upcoming addition of the nodemap logic, it's going to become more complicated. Being in the separate impl block has the advantage to be subject to rustfmt, whereas code inside macro calls isn't. Differential Revision: https://phab.mercurial-scm.org/D8153

revlog: using two new functions in C capsule from Rust code We expose `index_length` and `index_node` in the C capsule, so that the Rust representation of the C index can implement the `RevlogIndex` trait. Because our `Node` is actually a one-field struct, we have to decorate it for direct FFI exchange with the C `char*` It would be a good thing to get a length from the C layer, but doing so right now would probably interfere with the upcoming changes that will happen there for the hash length. Differential Revision: https://phab.mercurial-scm.org/D8152

nodemap: refresh the persistent data on nodemap creation The logic to read the data and validate the docket are still in python, so we need to "help" whatever compiled code live in the index to refresh it. Otherwise clearing the cache could lead to an expensive full recomputation and disk update even when the persisted data are still valid. Differential Revision: https://phab.mercurial-scm.org/D8174

tests: check availability of pyflakes by trying to import pyflakes module Since e397c6d74652, we use the pyflakes module instead of the pyflakes executable. As was pointed out during the review, the hghave check can be rewritten to try to import the pyflakes module instead of spawning a new subprocess.