A Git Hook Script to Block No-Fast-Forward Push

#!/bin/sh

# for details see here, http://git-scm.com/book/en/Customizing-Git-An-Example-Git-Enforced-Policy
# it seems that git on Windows doesn't support ruby, so use bash instead
# to function, put it into remote hook dir
# to disable, rename or delete file in remote hook dir

refname=$1
oldrev=$2
newrev=$3


# enforces fast-forward only pushes
check_fast_forward ()
{
  all_refs=`git rev-list ${oldrev}..${newrev} | wc  -l`
  single_parent_refs=`git rev-list ${oldrev}..${newrev} --max-parents=1 | wc  -l `
  if [ $all_refs -ne $single_parent_refs ]; then
    echo "Now not allow to push a non fast-forward reference."
    echo "If it cause any inconvenient, please tell."
    exit 1
  fi
}

check_fast_forward

Name the above script as “update”, and put it into remote repo’s “hooks” directory. If necessary, make it executable. With simple test, this hook works well for me. It DOES block a client pushing any merge commit (no-fast-forward commit) to remote repository, meanwhile allow fast-forward push, which together ensure a clean history in remote.

My first try was using a example script from this link. However, that didn’t work. If you have successfully used that script, maybe you give me some hints :-)

The above script is implemented by bash script, and also works on Windows. My original implementation was used ruby, but failed on Windows.

If you find any bug or improvement, please let me know. And have fun :-)