dispatch: add HGPLAIN=+strictflags to restrict early parsing of global options If this feature is enabled, early options are parsed using the global options table. As the parser stops processing options when non/unknown option is encountered, it won't mistakenly take an option value as a new early option. Still "--" can be injected to terminate the parsing (e.g. "hg -R -- log"), I think it's unlikely to lead to an RCE. To minimize a risk of this change, new fancyopts.earlygetopt() path is enabled only when +strictflags is set. Also the strict parser doesn't support '--repo', a short for '--repository' yet. This limitation will be removed later. As this feature is backward incompatible, I decided to add a new opt-in mechanism to HGPLAIN. I'm not pretty sure if this is the right choice, but I'm thinking of adding +feature/-feature syntax to HGPLAIN. Alternatively, we could add a new environment variable. Any bikeshedding is welcome. Note that HGPLAIN=+strictflags doesn't work correctly in chg session since command arguments are pre-processed in C. This wouldn't be easily fixed.

Our full contribution guidelines are in our wiki, please see:

https://www.mercurial-scm.org/wiki/ContributingChanges

If you just want a checklist to follow, you can go straight to

https://www.mercurial-scm.org/wiki/ContributingChanges#Submission_checklist

If you can't run the entire testsuite for some reason (it can be
difficult on Windows), please at least run `contrib/check-code.py` on
any files you've modified and run `python contrib/check-commit` on any
commits you've made (for example, `python contrib/check-commit
273ce12ad8f1` will report some style violations on a very old commit).