#!/bin/sh
#
# Copyright (c) 2005 Linus Torvalds
# Copyright (c) 2005 Junio C Hamano
#
. git-sh-setup || die "Not a git archive"

case "$0" in
*-revert* )
        me=revert ;;
*-cherry-pick* )
        me=cherry-pick ;;
* )
        die "What are ou talking about?" ;;
esac

usage () {
        case "$me" in
        cherry-pick)
                die "usage git $me [-n] [-r] <commit-ish>"
                ;;
        revert)
                die "usage git $me [-n] <commit-ish>"
                ;;
        esac
}

no_commit= replay=
while case "$#" in 0) break ;; esac
do
        case "$1" in
        -n|--n|--no|--no-|--no-c|--no-co|--no-com|--no-comm|\
            --no-commi|--no-commit)
                no_commit=t
                ;;
        -r|--r|--re|--rep|--repl|--repla|--replay)
                replay=t
                ;;
        -*)
                usage
                ;;
        *)
                break
                ;;
        esac
        shift
done

test "$me,$replay" = "revert,t" && usage

case "$no_commit" in
t)
        # We do not intend to commit immediately.  We just want to
        # merge the differences in.
        head=$(git-write-tree) ||
                die "Your index file is unmerged."
        ;;
*)
        head=$(git-rev-parse --verify HEAD) ||
                die "You do not have a valid HEAD"
        files=$(git-diff-index --cached --name-only $head) || exit
        if [ "$files" ]; then
                die "Dirty index: cannot $me (dirty: $files)"
        fi
        ;;
esac

rev=$(git-rev-parse --verify "$@") &&
commit=$(git-rev-parse --verify "$rev^0") ||
        die "Not a single commit $@"
prev=$(git-rev-parse --verify "$commit^1" 2>/dev/null) ||
        die "Cannot run $me a root commit"
git-rev-parse --verify "$commit^2" >/dev/null 2>&1 &&
        die "Cannot run $me a multi-parent commit."

# "commit" is an existing commit.  We would want to apply
# the difference it introduces since its first parent "prev"
# on top of the current HEAD if we are cherry-pick.  Or the
# reverse of it if we are revert.

case "$me" in
revert)
        git-rev-list --pretty=oneline --max-count=1 $commit |
        sed -e '
                s/^[^ ]* /Revert "/
                s/$/"/'
        echo
        echo "This reverts $commit commit."
        test "$rev" = "$commit" ||
        echo "(original 'git revert' arguments: $@)"
        base=$commit next=$prev
        ;;

cherry-pick)
        pick_author_script='
        /^author /{
                h
                s/^author \([^<]*\) <[^>]*> .*$/\1/
                s/'\''/'\''\'\'\''/g
                s/.*/GIT_AUTHOR_NAME='\''&'\''/p

                g
                s/^author [^<]* <\([^>]*\)> .*$/\1/
                s/'\''/'\''\'\'\''/g
                s/.*/GIT_AUTHOR_EMAIL='\''&'\''/p

                g
                s/^author [^<]* <[^>]*> \(.*\)$/\1/
                s/'\''/'\''\'\'\''/g
                s/.*/GIT_AUTHOR_DATE='\''&'\''/p

                q
        }'
        set_author_env=`git-cat-file commit "$commit" |
        sed -ne "$pick_author_script"`
        eval "$set_author_env"
        export GIT_AUTHOR_NAME
        export GIT_AUTHOR_EMAIL
        export GIT_AUTHOR_DATE

        git-cat-file commit $commit | sed -e '1,/^$/d'
        case "$replay" in
        '')
                echo "(cherry picked from $commit commit)"
                test "$rev" = "$commit" ||
                echo "(original 'git cherry-pick' arguments: $@)"
                ;;
        esac
        base=$prev next=$commit
        ;;

esac >.msg

# This three way merge is an interesting one.  We are at
# $head, and would want to apply the change between $commit
# and $prev on top of us (when reverting), or the change between
# $prev and $commit on top of us (when cherry-picking or replaying).

echo >&2 "First trying simple merge strategy to $me."
git-read-tree -m -u $base $head $next &&
result=$(git-write-tree 2>/dev/null) || {
    echo >&2 "Simple $me fails; trying Automatic $me."
    git-merge-index -o git-merge-one-file -a || {
            echo >&2 "Automatic $me failed.  After fixing it up,"
            echo >&2 "you can use \"git commit -F .msg\""
            case "$me" in
            cherry-pick)
                echo >&2 "You may choose to use the following when making"
                echo >&2 "the commit:"
                echo >&2 "$set_author_env"
            esac
            exit 1
    }
    result=$(git-write-tree) || exit
}
echo >&2 "Finished one $me."

# If we are cherry-pick, and if the merge did not result in
# hand-editing, we will hit this commit and inherit the original
# author date and name.
# If we are revert, or if our cherry-pick results in a hand merge,
# we had better say that the current user is responsible for that.

case "$no_commit" in
'')
        git-commit -n -F .msg
        rm -f .msg
        ;;
esac