'darcs copy' is like 'darcs move' but results in 2 files with the same patch
ancestory.

I have a large source file that is now too large to manage.  I wish to split it
into 2 'subfiles' that retain the origional history as they will both simply be
the origional large file, each with opposite halves of code removed.  I don't
want to have to be forced to choose which file should lose it's history.

On Tue, Dec 27, 2005 at 07:27:54PM +0000, Clive Crous wrote:
> 'darcs copy' is like 'darcs move' but results in 2 files with the same
> patch ancestory.

Unfortunately, this is quite tricky given the way darcs works, specifically
with regard to the invertibility of patches.  One could of course make a
darcs copy that is invertible, but it's hard to see how such a patch would
commute usefully with other patches.

I think that most likely an easier patch type would be a "split" patch,
which splits a file into two parts with no overlap.  It would still be
tricky, but would also be moderately straightforward.  It's closely related
to the "hunk move" patch idea, which would move a chunk of text from one
location to another within a given file.  One could achieve a "split" patch
by allowing a more general inter-file hunk move, which would be cool, but
would also be much harder to create a simple user interface for.  But then,
the interfile hunk move would allow you to maintain the history of a given
function even if it's moved from one file to another, so you'd potentially
gain a lot more than you do with the copy.

Even just the "simple" file split patch type would allow you to support
both file splitting and file joining operations.

In other words, this is a very interesting idea, but right now isn't the
time for it (or at least for me to work on it), and it requires some
thought.
-- 
David Roundy
http://www.darcs.net

Just for reference, here is an older discussion on RT

http://otherbugs.darcs.net//Ticket/Display.html?id=300