revert/shelf/undo/redo

[Michael Ellerman]

On Wed, 19 Oct 2005 13:12, Martin Pool wrote:
> mpe's shelf plugin (also in bzrtools) is very cool, and i encourage
> people who have not yet used it to try it out.  It shows all the
> changed diff hunks in the working tree and lets you choose which ones
> you would like to keep, and the others are set aside into .bzr-shelf.

Glad you like it :)

I've been thinking about shelf a bit lately, but haven't had any time to put 
any of my thoughts into code.

Basically I'd like a "shelf" to become a place where you can put multiple 
uncommited hunks, and/or commits. The default would be to shelve everything, 
the current behaviour would be selected with --hunks or --select.

Unshelve would then bring things off the shelf in reverse order (ie. LIFO), 
commits would be recommited, and uncommited hunks would just be left in the 
working tree.

Things that might be nice:
 - being able to "combine" two patches on the shelf, including combining
   non-adjacent patches. This could be tricky, but would be cool.
 - unshelving out of order. (similar problem)
 - when shelving commits, a choice of uncommiting them (ie. modifying history)
   or saving their inverse as a new commit.
 - being able to switch between multiple shelves.

That's probably all getting a bit ambitious, but we'll see.

A shelf with (some of) these properties would basically be an implementation 
of quilt in bzr. Having used quilt for a while, I think for some workflows 
the "tree + patches" model is valuable.

> We also have 'bzr revert' which undoes all changes to reset the
> directory back to the previous revision.  As has been recently
> discussed, this has some risk of destroying user data.  To fix the
> most immediate problem we should probably give revert an option that
> says whether newly-added files should be deleted or just unversioned.

And it shouldn't be the default.

> [re undo] ...

I'm not sure about undo. I think it could be cool, as long as *all operations* 
that affect the repository are undoable. So that includes: adds and removes, 
commits, pulls, merges, ignores (?) ... it could get tricky. What you don't 
want is for the user to think "bzr undo will undo X" and for it to actually 
do Y, especially when X is a subset of Y.

> It would be nice to factor out the hunk-picking parts of shelve and
> make them reusable by this and perhaps by 'commit --interactive'.

I think that code's reasonable, it does nasty things to the terminal though, 
so we'd need to make sure it plays nice with the rest of bzr.

cheers

-- 
Michael Ellerman
IBM OzLabs

email: michael:ellerman.id.au
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