[Haskell-cafe] Why not Darcs?

[Jason Dagit]

On Thu, Apr 21, 2011 at 8:42 PM, John Millikin <jmillikin at gmail.com> wrote:

> On Thursday, April 21, 2011 4:16:07 PM UTC-7, John Meacham wrote:
>>
>> Um, the patch theory is what makes darcs "just work". There is no need
>> to understand it any more than you have to know VLSI design to
>> understand how your computer works. The end result is that darcs
>> repositories don't get corrupted and the order you integrate patches
>> doesn't affect things meaning cherrypicking is painless.
>
>
> This is how it's *supposed* to work. My chief complaints with PT are:
>
>    - Metadata about branches and merges gets lost. This makes later
>    examination of the merge history impossible, or at least unfeasibly
>    difficult.
>
> That's not an issue with patch theory though.  Darcs could still track that
and I believe some people have been playing with the idea.


>
>    - Every commit needs --ask-deps , because the automatic dependency
>    detector can only detect automatic changes (and not things like adding a new
>    function in a different module)
>
>
You mean it can only detect dependencies that depend on each other with
respect to a diff of the changes.  Detecting most anything else would be
undecidable in the general case.  As a divergent data point, I've been using
darcs since 2003 and I have yet to use --ask-deps except to learn how it
works.


>    - The order patches are integrated still matters (it's impossible for
>    it to not matter), but there's no longer any direct support for ordering
>    them, so large merges become very manual.
>
>
Can you give an example where you need to control the order of the changes
in a merge with git/bzr/svn/etc but that it was not possible with darcs?
 I'm trying to understand what you mean.


>
>    - If you ever merge in the wrong order, future merges will begin
>    consuming more and more CPU time until the repository "dies". Undoing this
>    requires using darcs-fastconvert and performing manual surgery on the export
>    files.
>
>
Yes, this is true.  Exponential merges still exist, although they are
relatively rare with a darcs-2 formated repository.

Jason
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