list all branch name for repo command

如果 .git 資料夾下有FETCH_HEAD，可以用下面方法列出所有branch name

cat $(./repo list | awk -F " : " '{printf("%s/.git/FETCH_HEAD\n", $1)}')

cat $(./repo list | awk -F " : " '{printf("%s/.git/FETCH_HEAD\n", $1)}') | cut -b 41-