def robotsrulesetOfDomain(self, domain):
		'''检查domain是否在数据库中,
			否 --> (False, None)
			是 --> (True, 数据库中存储的robots.txt内容)
		'''
		exist = False
		cur = self.conn.cursor()
		# 是否存在
		cur.execute("SELECT 1 FROM Domains WHERE domain=?", (domain,))
		if cur.fetchone() :
			exist = True
		# 存在的话,结果是什么
		cur.execute("SELECT rules FROM Domains,Rulesets "
			"WHERE domain=? AND Domains.did=Rulesets.did"
			,(domain,) )
		ruleset = cur.fetchone()
		return (exist, ruleset)
def get_git_version(self):
        VERSION_PFX = 'git version '
        version = self.run_command(
            ['version'], show_stdout=False, stdout_only=True
        )
        if version.startswith(VERSION_PFX):
            version = version[len(VERSION_PFX):].split()[0]
        else:
            version = ''
        # get first 3 positions of the git version because
        # on windows it is x.y.z.windows.t, and this parses as
        # LegacyVersion which always smaller than a Version.
        version = '.'.join(version.split('.')[:3])
        return parse_version(version)