Re: [RFC] undo and redo

> Hello,
> 
> So, one thing that I liked about GNU Arch when I tried it out was the
> ability to undo and redo changes in the local working copy.  I decided
> to try to do this with git.  What I have is preliminary.  I'm sure it
> could use some work.
> 
> So, I started with the assumption that all changes in the working copy
> have been updated to the cache.  My scripts check this (with
> git-diff-files) and abort if this is not the case.
> 
> Undo calls git-write-tree to write the changes to the object store.  It
> stores that tree's hash and the current HEAD's tree's hash in a file.
> Then it reverts the working copy to HEAD.
> 
> Redo grabs these two trees from the file, does git-write-tree to produce
> a third tree and merges the three using the old HEAD's tree as the base
> of the merge.  This way, new commits can happen and the local copy can
> be modified since the undo and it should still work assuming no
> conflicts emerge.
> 
> Attached are the two scripts.  Comments and criticism are welcome.
> 
> Cheers,
> Carl
> 
> -- 
> - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
>  Carl Baldwin                        Systems VLSI Laboratory
>  Hewlett Packard Company
>  MS 88                               work: 970 898-1523
>  3404 E. Harmony Rd.                 work: Carl.N.Baldwin@hp.com
>  Fort Collins, CO 80525              home: Carl@ecBaldwin.net
> - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -

> #!/bin/sh
> 
> . git-sh-setup-script || die "Not a git archive"
> 
> if [ -n "$(git-diff-files)" ]; then
>     echo The following files should be updated!
>     echo
>     git-diff-files | awk '{print $6}'
> fi
> 
> undostack=$GIT_DIR/undostack
> 
> if [ ! -s $undostack ]; then
>     echo "No undo information in $undostack"
> else
>     # Read the top of the stack
>     basetree=$(cat $undostack | tail -n 2 | head -n 1)
>     redotree=$(cat $undostack | tail -n 1)
> 
>     # Pop the stack
>     cat $undostack | head -n -2 > $undostack.tmp
>     mv $undostack{.tmp,}
> 
>     currenttree=$(git-write-tree)
> 
>     git-read-tree -u -m $basetree $currenttree $redotree
>     git-merge-cache git-merge-one-file-script -a
> fi

> #!/bin/sh
> 
> . git-sh-setup-script || die "Not a git archive"
> 
> if [ -n "$(git-diff-files)" ]; then
>     echo The following files should be updated!
>     echo
>     git-diff-files | awk '{print $6}'
> fi
> 
> undostack=$GIT_DIR/undostack
> 
> headtree=$(git-cat-file commit $(cat $GIT_DIR/HEAD) | head -n 1 | sed -e 's/tree //')
> undotree=$(git-write-tree)
> 
> if [ $headtree == $undotree ]; then
>     echo There are no changes to undo.
> else
>     {
>        echo $headtree
>        echo $undotree
>     } >> $undostack
> 
>     echo Saved current state as tree $undotree.
>     echo Reverting to HEAD, $headtree...
> 
>     git-checkout-script -f
> fi