#!/bin/sh
# Copyright (c) 2007, Nanako Shiraishi

USAGE='[ | list | show | apply | clear]'

SUBDIRECTORY_OK=Yes
. git-sh-setup
require_work_tree

TMP="$GIT_DIR/.git-stash.$$"
trap 'rm -f "$TMP-*"' 0

ref_stash=refs/stash

no_changes () {
        git diff-index --quiet --cached HEAD &&
        git diff-files --quiet
}

clear_stash () {
        logfile="$GIT_DIR/logs/$ref_stash" &&
        mkdir -p "$(dirname "$logfile")" &&
        : >"$logfile"
}

save_stash () {
        stash_msg="$1"

        if no_changes
        then
                echo >&2 'No local changes to save'
                exit 0
        fi
        test -f "$GIT_DIR/logs/$ref_stash" ||
                clear_stash || die "Cannot initialize stash"

        # state of the base commit
        if b_commit=$(git rev-parse --verify HEAD)
        then
                head=$(git log --abbrev-commit --pretty=oneline -n 1 HEAD)
        else
                die "You do not have the initial commit yet"
        fi

        if branch=$(git symbolic-ref -q HEAD)
        then
                branch=${branch#refs/heads/}
        else
                branch='(no branch)'
        fi
        msg=$(printf '%s: %s' "$branch" "$head")

        # state of the index
        i_tree=$(git write-tree) &&
        i_commit=$(printf 'index on %s' "$msg" |
                git commit-tree $i_tree -p $b_commit) ||
                die "Cannot save the current index state"

        # state of the working tree
        w_tree=$( (
                rm -f "$TMP-index" &&
                cp -p ${GIT_INDEX_FILE-"$GIT_DIR/index"} "$TMP-index" &&
                GIT_INDEX_FILE="$TMP-index" &&
                export GIT_INDEX_FILE &&
                git read-tree -m $i_tree &&
                git add -u &&
                git write-tree &&
                rm -f "$TMP-index"
        ) ) ||
                die "Cannot save the current worktree state"

        # create the stash
        if test -z "$stash_msg"
        then
                stash_msg=$(printf 'WIP on %s' "$msg")
        else
                stash_msg=$(printf 'On %s: %s' "$branch" "$stash_msg")
        fi
        w_commit=$(printf '%s\n' "$stash_msg" |
                git commit-tree $w_tree -p $b_commit -p $i_commit) ||
                die "Cannot record working tree state"

        git update-ref -m "$stash_msg" $ref_stash $w_commit ||
                die "Cannot save the current status"
        printf >&2 'Saved "%s"\n' "$stash_msg"
}

have_stash () {
        git rev-parse --verify $ref_stash >/dev/null 2>&1
}

list_stash () {
        have_stash || return 0
        git log --pretty=oneline -g "$@" $ref_stash |
        sed -n -e 's/^[.0-9a-f]* refs\///p'
}

show_stash () {
        flags=$(git rev-parse --no-revs --flags "$@")
        if test -z "$flags"
        then
                flags=--stat
        fi
        s=$(git rev-parse --revs-only --no-flags --default $ref_stash "$@")

        w_commit=$(git rev-parse --verify "$s") &&
        b_commit=$(git rev-parse --verify "$s^") &&
        git diff $flags $b_commit $w_commit
}

apply_stash () {
        git diff-files --quiet ||
                die 'Cannot restore on top of a dirty state'

        unstash_index=
        case "$1" in
        --index)
                unstash_index=t
                shift
        esac

        # current index state
        c_tree=$(git write-tree) ||
                die 'Cannot apply a stash in the middle of a merge'

        s=$(git rev-parse --revs-only --no-flags --default $ref_stash "$@") &&
        w_tree=$(git rev-parse --verify "$s:") &&
        b_tree=$(git rev-parse --verify "$s^:") ||
                die "$*: no valid stashed state found"

        test -z "$unstash_index" || {
                git diff --binary $s^2^..$s^2 | git apply --cached
                test $? -ne 0 &&
                        die 'Conflicts in index. Try without --index.'
                unstashed_index_tree=$(git-write-tree) ||
                        die 'Could not save index tree'
                git reset
        }

        eval "
                GITHEAD_$w_tree='Stashed changes' &&
                GITHEAD_$c_tree='Updated upstream' &&
                GITHEAD_$b_tree='Version stash was based on' &&
                export GITHEAD_$w_tree GITHEAD_$c_tree GITHEAD_$b_tree
        "

        if git-merge-recursive $b_tree -- $c_tree $w_tree
        then
                # No conflict
                a="$TMP-added" &&
                git diff --cached --name-only --diff-filter=A $c_tree >"$a" &&
                git read-tree --reset $c_tree &&
                git update-index --add --stdin <"$a" ||
                        die "Cannot unstage modified files"
                git-status
                rm -f "$a"
                test -z "$unstash_index" || git read-tree $unstashed_index_tree
        else
                # Merge conflict; keep the exit status from merge-recursive
                status=$?
                test -z "$unstash_index" || echo 'Index was not unstashed.' >&2
                exit $status
        fi
}

# Main command set
case "$1" in
list)
        shift
        if test $# = 0
        then
                set x -n 10
                shift
        fi
        list_stash "$@"
        ;;
show)
        shift
        show_stash "$@"
        ;;
apply)
        shift
        apply_stash "$@"
        ;;
clear)
        clear_stash
        ;;
help | usage)
        usage
        ;;
*)
        if test $# -gt 0 && test "$1" = save
        then
                shift
        fi
        save_stash "$*" && git-reset --hard
        ;;
esac