[PATCH 3 of 3] copies: do not track backward copies, only renames (issue3739)

[Matt Mackall]

On Fri, 2012-12-21 at 19:50 -0800, Siddharth Agarwal wrote:
> On 12/21/2012 03:42 PM, Matt Mackall wrote:
> > All of this is a long way of saying that I don't think your commit 
> > comment is correct. 
> 
> Thanks for the correction. I agree that "ypoc" is something we should 
> eventually handle, perhaps with a richer data structure that supports 
> the full range of possibilities. What do you think of keeping the code 
> the same, but updating the commit message to:
> 
> copies: do not track backward copies, only renames (issue3739)
> 
> The inverse of a rename is a rename, but the inverse of a copy is not a 
> copy.
> Presenting it as such -- in particular, stuffing it into the same dict 
> as real
> copies -- causes bugs because other code starts believing the inverse copies
> are real.
> 
> The only test whose output changes is test-mv-cp-st-diff.t. When a backwards
> status -C command is run where a copy is involved, the inverse copy 
> (which was
> hitherto presented as a real copy) is no longer displayed.
> 
> Keeping track of inverse copies is useful in some situations -- 
> composability
> of diffs, for example, since a delete of "b" followed by an inverse copy "b"
> to "a" is equivalent to a rename "b" to "a". However, representing them 
> would
> require a more complex data structure than the same dict in which real 
> copies
> are also stored.

Seems fine.

-- 
Mathematics is the supreme nostalgia of our time.