cmdutil: change check_incompatible_arguments() *arg to single iterable This makes it clearer on the call-sites that the first argument is special. Thanks to Yuya for the suggestion. Differential Revision: https://phab.mercurial-scm.org/D8018

rust: remove an unnecessary set of parentheses My build complained about this. I guess it started after I upgraded rustc. Differential Revision: https://phab.mercurial-scm.org/D8020

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.