profiling: flush stdout before writing profile to stderr On py3, stdout and stderr appear to be buffered and this causes my command's output to be intermixed with the profiling output. Differential Revision: https://phab.mercurial-scm.org/D8024

rust: re-format with nightly rustfmt This fixes test-check-rust-format.t. Differential Revision: https://phab.mercurial-scm.org/D8025

tests: stablize test-rename-merge1.t on Windows This goes with d7622fdec3b5. Differential Revision: https://phab.mercurial-scm.org/D8036

rust-cpython: make sure PySharedRef::borrow_mut() never panics Since it returns a Result, it shouldn't panic depending on where the borrowing fails. PySharedRef::borrow_mut() will be renamed to try_borrow_mut() by the next patch.

rust-cpython: remove useless wrappers from PyLeaked, just move by map() This series prepares for migrating to the upstreamed version of PySharedRef. I found this last batch wasn't queued while rewriting the callers. While Option<T> was historically needed, it shouldn't be required anymore. I wasn't aware that each filed can be just moved.

rust-node: avoid meaningless read at the end of odd prefix This should be heavily factored out by the CPU branch predictor anyway. Differential Revision: https://phab.mercurial-scm.org/D8019

rust-nodemap: generic NodeTreeVisitor This iterator will help avoid code duplication when we'll implement `insert()`, in which we will need to traverse the node tree, and to remember the visited blocks. The structured iterator item will allow different usages from `lookup()` and the upcoming `insert()`. Differential Revision: https://phab.mercurial-scm.org/D7794