unbundle: add a small comment to clarify the 'check_heads' call
Bundle2 has its own mechanisms to check for heads (and other) changes, so push
using bundle2 is relying on the "check:heads" bundle part of unbundle and the
'check_heads' call is not checking anything. We add a small comment to make
this clearer.
#require docutils gettext
$ $TESTDIR/check-gendoc el
checking for parse errors