evolve: extract logic of pre-checking divergence risk to its own function Extracting the logic (which is used to check if rewriting an obsolete revision will create divergence) to a function. This function will be used in upcoming patches of pre-checking. This is how we check if rewriting an obsolete revision will create divergence. We need to check two cases: If there is any 1) non-obsolete successor. -> easily done by `obsutil.successorssets()` 2) precursor with non-obsolete successor. -> using `evolvecmd.divergentsets()`

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