Flags after `--` should not be effective. That`s a universal rule across
common software. People should be able to hg log a file named `--debugger`.
Besides, hg ... -- --profile --traceback` should not enable profiling or
traceback.
This patch changes the handling of `--debugger`, `--profile`, `--traceback`
so they are ineffective after `--`. This makes other software easier to deal
with command line flags injection by adding `--` before user input. See
https://hackerone.com/reports/288704
Those flags are only used for developers. So this BC looks fine.
.. bc::
Certain global flags (`--debugger`, `--profile`, and `--traceback`) are
no longer effective after `--`.