discovery: do not build sample if undecided is smaller than sample size
This prevents crash with coming change in the mercurial discovery.
recursive-include docs/figures *.svg
include docs/figures/hgview-example.png
include docs/*.rst
include docs/*.py
include docs/tutorials/*.t
include docs/makefile
include docs/static/*.svg
include hgext/__init__.py
include hgext/evolve.py
include hgext/pushexperiment.py
include hgext/simple4server.py
include setup.py
include README
include COPYING
include tests/*.t
include tests/*.py
include tests/_exc-util.sh
include tests/dummyssh
exclude tests/test-oldconvert.t
exclude tests/test-qsync.t
exclude tests/test-drop.t