#!/bin/sh

# Helper hook to prevent folk from accidentally committing broken Puppet 
# manifests to the repository.
#
# You must have Ruby and Puppet installed on your workstation.  If a 
# local copy of the `puppet' program is not available, and you know what 
# you are doing, you may bypass this hook script at your own peril with:
#
#     $ git config anchor.im_a_puppet_master true
#
# or, for a once-off display of intrepidity, `git commit --no-verify'.

derp() {
    echo "[$(basename ${0})] ${@}"
    exit 1
}

if git rev-parse --verify HEAD >/dev/null 2>&1; then
    against=HEAD
else
    # Initial commit: diff against an empty tree object
    against=4b825dc642cb6eb9a060e54bf8d69288fbee4904
fi

if [ "$(git config anchor.im_a_puppet_master)" = 'true' ]; then
    # User has opted out of manifest verification
    exit 0
fi

if which puppet >/dev/null 2>&1; then
    # Find the root of the Git repository.  The paths `git diff' spits 
    # out will be relative to this root.
    OLD_PWD="$PWD"
    while [ \! -d .git ]; do
        if [ "$PWD" = "/" ]; then
            cd "$OLD_PWD"
            derp "I could not find the root of your Git repo."
        fi
        cd ..
    done
    IFS='
'
    boned=0
    for MANIFEST in $(git diff --cached --name-only --diff-filter=AM \
      $against | grep '\.pp$'); do
        puppet --parseonly "$MANIFEST" || boned=1
    done
    cd "$OLD_PWD"
    if [ $boned -ne 0 ]; then
        derp "Aborting on broken manifest.  See feedback above."
    fi
else
    cat - <<EOF
Hey!  You don't have Puppet installed on your workstation!

Installing Puppet will allow me to automatically check your work for 
common typographical errors.  Without this check, your (potentially) 
broken manifests will make it out into the wild.  You will be left to 
waste your own time following-up with a correction, a new commit, and 
another roll-out.

If you would like to proceed anyway, punch this into your shell, and 
commit again:

    git config anchor.im_a_puppet_master true

EOF
    derp "Aborting your commit because I could not find puppet."
fi