ui: actually return a value for `_fout_is_a_tty()`
ui: avoid a str interpolation into bytes crash in `fixconfig()`
run-tests: attempt to use `hg.bat` in pure mode
run-tests: fix `--hg-wheel` semantics when not in the repo root
test-run-test: prevent `pip` from caching items in the repo root
tests: disable color for `hg fastexport` with redirected output (again)
revlogutils: reorder the open mode for `debug::fast-upgrade` to appease C code
tests: stabilize test-branch-change.t on Windows