I work with a git repository via TRAMP (and magit, but that doesn't seem
to be important).  Repository's owner is user x, and x's umask is 022.
All operations on the repository are done via /sudo:x@.../ My umask,
however, is 077.  I can't make Emacs use a umask that would be
appropriate to the context.  It seems to always use a global umask.

I searched the mailing list, found this thread
https://lists.gnu.org/archive/html/help-gnu-emacs/2016-06/msg00214.html
It resolves with the recommendation to use
tramp-handle-write-region-hook.  With git repository, this won't help as
operations are performed by git.  E.g. a rebase messes up everything.

There is another suggestion there that recommends to alter x's .profile
and set umask depending on a value passed via
tramp-remote-process-environment.  I just altered x's .profile to set
umask *unconditionally*, and it has no effect.  So far, the way Tramp
treats umask makes absolutely no sense to me.

What are my options?