Problem:
nvim_win_set_buf() on a non-current win, while the current win has
a win-local dir, changes the global CWD:
:vsplit | lcd ..
:call nvim_win_set_buf(other_win, buf)
:wincmd l
:verbose pwd
[global] /parent " expected: the initial cwd
Analysis:
`globaldir` is where to return when no local dir applies; NULL means the
process CWD is already there. Switching to a window with no local dir
makes update_cwd() chdir back to `globaldir` and clear it. kCtxKeepCwd
restores the process CWD but not that bookkeeping, so the restored
window-local dir is mistaken for the global one.
Solution:
Save/restore `globaldir` with the CWD.
cd2db7913a