How to control merge behavior in git

Question

Assume that there are two branches A and B in the git library. How to set it to achieve the following effect: B merge into A is allowed, and vice versa is not allowed.

高洛峰 · Answer

vi .git/hooks/prepare-commit-msg

#!/bin/sh
case "," in
    merge,)
        grep "'A'" ; 
        if [ $? ];then
            echo '禁止合并A merge into B';
            exit 1;
        fi;;
  *) ;;
esac