在安装open-falcon的nodata组件，更新库的时候，git pull 报错：
You are not currently on a branch, so I cannot use any
'branch.<branchname>.merge' in your configuration file.
Please specify which branch you want to merge with on the command
line and try again (e.g. 'git pull <repository> <refspec>').
解决办法：
首先git checkout -b temp
其次git checkout master
即可恢复到master repository的状态，然后就可以pull了