Re: [RFC] undo and redo

Well, both are good ideas.  Both are stack oriented, though.

I see what you mean about adding an undo directory to .git/refs/. I will do some tests... (read further)

On Wed, Aug 24, 2005 at 03:48:21PM -0700, Junio C Hamano wrote:

So, I've tried cloning, pulling to|from, pushing to|from and resolving merges in a repository with undo information stored under .git/refs/undo. None of these operations seem to notice the existence of this directory. I think this is good.

The cloned repository does not end up 'inheriting' the undo directory (as I would expect) but does end up with any objects reachable from the undo tree. However, these objects get pruned on the next 'git prune'. This, I think, is minor.

Pull seems to ignore the undo directory and, of course, the objects reachable by the undo trees. This is what I expected and wanted.

Resolving merges worked as expected.

I think undo trees should be considered local to the repository and this is the behavior that I observed. I think this is a positive.

Before reading your message, I polished up the scripts and changed them so that they store the undo tree and the base tree's hashes in the .git/refs/undo directory. Also, git-redo-script can take an optional argument...the name of the undo to replay. I guess undo should also take an optional argument to give the undo tree some symbolic name.

I think this is getting rather solid.  Let me know what you think.

Here is the git-undo-script:

#!/bin/sh

. git-sh-setup-script || die "Not a git archive"

git-update-cache --refresh || exit 1

undodir=$GIT_DIR/refs/undo

undoinfo=$undodir/$(date +%Y.%m.%d.%H.%M.%S)

headtree=$(git-cat-file commit $(cat $GIT_DIR/HEAD) | sed -n 's/^tree //p') undotree=$(git-write-tree)

if [ $headtree == $undotree ]; then
    echo There are no changes to undo.
else
    mkdir -p $(dirname $undoinfo)
    echo $headtree > $undoinfo.base
    echo $undotree > $undoinfo.undo

    echo Saved current state in $undodir as $(basename $undoinfo)

    git-read-tree -m -u $undotree $headtree
fi

# --- SNIP ---

and here, is the redo script

#!/bin/sh

. git-sh-setup-script || die "Not a git archive"

git-update-cache --refresh || exit 1

usage () {
    echo >&2 "Usage: git-redo-script [undo name]"
    exit 1
}

undodir=$GIT_DIR/refs/undo

# If an 'undo name' was given on the command line then try to use it.
# If not, then automatically pick the most recent undo.
undoinfo=
case "$#" in
0)
    undoinfo=$undodir/$(ls -tr $undodir | sed -n 's/\.undo$//p' | tail -n 1)
    ;;
1)
    if [ -s $undodir/$1 ]; then
        undoinfo=$(echo $undodir/$1 | sed -n "s/\.[^.]*$//p")
    elif [ -s $undodir/$1.undo -a -s $undodir/$1.base ]; then
        undoinfo=$undodir/$1
    else
        usage
    fi
    ;;
*)
    usage
    ;;
esac

# Perform a three-way merge between the base tree, undo tree and current index
if [ ! -s $undoinfo.undo -o ! -s $undoinfo.base ]; then
    echo "No undo information available"
else
    git-read-tree -u -m $(cat $undoinfo.base) $(cat $undoinfo.undo) $(git-write-tree)
    git-merge-cache git-merge-one-file-script -a

    rm -f $undoinfo.*
    test -z "$(ls $undodir)" && rmdir $undodir
fi

# --- SNIP ---

I would be glad to write up documentation and provide a patch.

Cheers, Carl