Re: Git merge tool for Org files

[Achim Gratz <Stromeko@nexgo.de>]

Carsten Dominik <carsten.dominik@gmail.com> writes:
> One of the obstacle for using Org-mode for collaborative programs is
> that many operations add or remove text from the beginning or end of a
> file, or which add or remove a subnode from an outline tree.

On of the things that I think would be necessary is a way to put an Org
document into a "normalized" representation and then evaluate the
differences between two of these.  The generic exporter started by
Bastien could probably deliver such a representation.

> These are operations that confuse the git merger, in particular
> if two people have added something to a file, or removed/added
> sequential sibling nodes.

Git merge only works reasonably well for program code (and only if
there's no changelog stuff inside the file).  The merge driver
functionality is there to solve that problem for when you _can_ be
smarter.  It is absolutely not necessary to write that driver in any
particular language, all that git does is to call the driver with three
versions of the same file as the argument.

> I believe that this could be solved with a dedicated merge driver
> that understands the integrity of an outline (sub)tree, and that
> knows that the sequence of two new subtrees added by different people
> does not matter.

You ask a potentially very big question here, this should be constrained
to keep it manageable.  I think a reasonable strategy is to merge two
Org documents "from the outside in", that is starting with the topmost
tree elements.  If you are merging at the tree level, anything inside
the tree should not matter at all.  I'm not sure the sequence doesn't
matter, but that can hardly be decided by the merge driver unless it
figures out how to sort elements of a tree.  The second step would then
be to check the leaf nodes of the tree for concurrent changes, which
probably still need to be resolved manually.


Regards,
Achim.
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