#!/usr/bin/env bash
# reset environment variables that could interfere with normal usage
export GREP_OPTIONS=
# put all utility functions here

# make a temporary file
git_extra_mktemp() {
    mktemp -t "$(basename "$0")".XXXXXXX
}

git_extra_default_branch() {
    local default_branch
    default_branch=$(git config --get git-extras.default-branch)
    if [ -z "$default_branch" ]; then
        echo "master"
    else
        echo "$default_branch"
    fi
}
#
# check whether current directory is inside a git repository
#

is_git_repo() {
  git rev-parse --show-toplevel > /dev/null 2>&1
  result=$?
  if test $result != 0; then
    >&2 echo 'Not a git repo!'
    exit $result
  fi
}

is_git_repo

# Warn on a dirty work tree.
git rev-parse --verify HEAD >/dev/null || exit 1
git update-index -q --ignore-submodules --refresh
if ! git diff-files --quiet --ignore-submodules
then
        echo "WARNING (dirty work tree): The patch will only be checked against actual commits."
fi

# Warn on a dirty index.
if ! git diff-index --cached --quiet --ignore-submodules HEAD --
then
        echo "WARNING (dirty index): The patch will only be checked against actual commits."
fi

# Use a temporary index.
index=$(git_extra_mktemp)
cleanup() {
        rm $index
        exit 2
}
trap cleanup 2

# Go back in history while parent commits are available.
echo "Trying to find a commit the patch applies to..."
rev=$(git rev-parse HEAD)
while [ $? = 0 ]
do
        GIT_INDEX_FILE=$index git read-tree $rev

        # Try to apply the patch.
        GIT_INDEX_FILE=$index git apply --cached $1 >/dev/null 2>&1
        patch_failed=$?

        # Do it again, but show the error, if the problem is the patch itself.
        if [ $patch_failed = 128 ]
        then
                GIT_INDEX_FILE=$index git apply --index --check $1
                exit $patch_failed
        fi

        # The patch applied. Commit and rebase.
        if [ $patch_failed = 0 ]
        then
                # Manufacture a commit.
                tree=$(GIT_INDEX_FILE=$index git write-tree)
                commit=$(git commit-tree $tree -p $rev -m "$1")
                rm $index

                echo "Patch applied to $(git rev-parse --short $rev) as $(git rev-parse --short $commit)"

                git cherry-pick $commit
                exit $?
        fi

        rev=$(git rev-parse --verify -q $rev^)
done

# No compatible commit found. Restore.
echo "Failed to find a commit the patch applies to."
rm $index
exit 1
