chg: make `chg --cwd $anything -R $relativepath` behave better We're seeing this kind of issue: ``` $ (cd repo1; chg --cwd ../repo2 -R .) chg: abort: too many redirections. Please make sure $path/hg is not a wrapper which changes sensitive environment variables before executing hg. If you have to use a wrapper, wrap chg instead of hg. [255] ``` chgserver is interpreting -R as relative to its cwd, instead of relative to --cwd like regular hg does, which I think causes an inconsistency leading to the above. Differential Revision: https://phab.mercurial-scm.org/D12579