[Haskell-cafe] A small Darcs anomoly

[Andrew Coppin]

I've discovered something interesting.

Darcs stores history as a partially-ordered set of changes. This is a 
beautiful and elegant idea. In theory, this lets me apply any 
combination of changes, possibly generating file "versions" which have 
never actually existed before. (E.g., the new type checker from GHC 7.0 
embedded in the GHC 6.6 codebase - not that I imagine it would compile, 
but in principle I can do it.)

So I was a little surprised to discover that... Darcs doesn't actually 
support doing this. Darcs is only really interested in the result of 
applying *all* changes in a repo. If you want to apply some subset of 
changes, you need to make a seperate repo containing only the changes 
you want applied.

It seems daft to me that you would design a sophisticated system for 
splitting history into independent chunks, and then not let me 
manipulate them independently.

(If you think about it, the difference between, say, GHC 7.0 and GHC 6.6 
is which set of changes are applied. Yet because Darcs doesn't support 
looking at it like this, you must have a completely seperate repo for 
each one...)