git 相关变量和概念

https://jasoncodes.com/posts/gup-git-rebase

BRANCH=$(git symbolic-ref -q HEAD)

BRANCH=${BRANCH##refs/heads/}

BRANCH=${BRANCH:-HEAD}

输出:

+ BRANCH=refs/heads/master

+ BRANCH=master

+ BRANCH=master

if [ -z "$(git config branch.$BRANCH.remote)" -o -z "$(git config branch.$BRANCH.merge)" ]

输出 (从 .git/config 文件中读取出来的):

++ git config branch.master.remote

++ git config branch.master.merge

+ '[' -z origin -o -z refs/heads/master ']'

HEAD detached from origin/a-trade-dby-20161111-1129

说明HEAD已经被重指向, http://blog.csdn.net/trochiluses/article/details/8991701.
查看当前HEAD