push: extract obsmarkers discovery in a dedicated function The need to factorise the computation of the markers to send in a dedicated function. This prepare the inclusion of obsmarkers in an atomic bundle2 push. For now, when obsmarkers are pushed using bundle2, they are still doing it on their own, in a dedicated bundle2 push.

syntax: re
/figures/[^/]+\.png$
^docs/build/
^docs/html/
^html/
\.pyc$
~$
\.swp$
\.orig$
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\.err$
^tests/easy_run.sh$
^build/
^MANIFEST$
^docs/tutorials/.*\.rst$
\.ico$