builddependencies: extract function for getting successors
The code no longer makes a difference between single- and
mult-successor cases and just needs a set (or generator, really) of
successors to iterate over. Let's extract that into a function.
import hghave
@hghave.check("docgraph-ext", "Extension to generate graph from repository")
def docgraph():
try:
import hgext.docgraph
hgext.docgraph.cmdtable # trigger import
except ImportError:
try:
import hgext3rd.docgraph
hgext3rd.docgraph.cmdtable # trigger import
except ImportError:
return False
return True