#!/bin/sh

# Remove a Git hook with a given MD5 hash from the user's .git/hooks/
# directory.
#
# Usage:
#   remove-hook <hook-file> <MD5 hash>
# Example:
#   remove-hook prepare-commit-msg c3532e525137bd49ac4d9bcde8391e54


# Require exactly one argument that does not start with a '-'
if [ "$#" != '2' -o "$(echo "$1" | cut -c1)" = '-' \
                 -o "$(echo "$2" | cut -c1)" = '-' ]; then
    echo "remove-hook: Remove a Git hook with a given MD5 hash from the user's .git/hooks/ directory."
    echo 'Usage:'
    echo '  remove-hook <hook-file> <MD5 hash>'
    exit 1
fi


hash_content() {
    # Print a hash of a file's content
    filename="$1"
    md5sum "${filename}" | cut -d ' ' -f 1
}


find_git_root() {
    # Find the directory containing our .git directory.
    # Resolves 'git worktree' indirection.
    # Prints nothing if the cwd is not under Git
    git_root="$(git rev-parse --show-toplevel 2>/dev/null)"
    if [ ! "${git_root}" ]; then
        return
    fi
    dot_git="${git_root}/.git"
    if [ -d $dot_git ]; then
        echo $git_root
    else
        # 'git worktree': .git points to the true root dir
        cat $dot_git \
            | grep -E '^gitdir:' \
            | sed -r -e 's/^gitdir:\s*//;' -e 's|/\.git/worktrees/.*||;'
    fi
}


hook_name="$1"
md5hash="$2"

git_root="$(find_git_root)"
if [ ! "${git_root}" ]; then
    echo "Not a Git repository -- not attempting to remove hook"
    exit 0
fi

hook="${git_root}/.git/hooks/${hook_name}"

if [ ! -e "${hook}" ]; then exit 0; fi

if [ ! -r "${hook}" ]; then
    echo "Hook ${hook} is not readable -- not attempting to remove hook"
    exit 1
fi

if [ "$(hash_content ${hook})" != "${md5hash}" ]; then
    echo "MD5 sums do not match -- not removing hook"
    exit 0
fi

echo "Removing hook ${hook}"
rm "${hook}"