req_install.py 文件源码

def update_editable(self, obtain=True):
        if not self.link:
            logger.debug(
                "Cannot update repository at %s; repository location is "
                "unknown",
                self.source_dir,
            )
            return
        assert self.editable
        assert self.source_dir
        if self.link.scheme == 'file':
            # Static paths don't get updated
            return
        assert '+' in self.link.url, "bad url: %r" % self.link.url
        if not self.update:
            return
        vc_type, url = self.link.url.split('+', 1)
        backend = vcs.get_backend(vc_type)
        if backend:
            vcs_backend = backend(self.link.url)
            if obtain:
                vcs_backend.obtain(self.source_dir)
            else:
                vcs_backend.export(self.source_dir)
        else:
            assert 0, (
                'Unexpected version control type (in %s): %s'
                % (self.link, vc_type))