[darcs-devel] [issue986] Darcs issues with the GHC repository

[Jason Dagit]

New submission from Jason Dagit <dagit at codersbase.com>:

These are Simon Marlow's notes on areas that darcs needs to improve on to be
useful for GHC:

I promised to put together our reasoning on why we don't think moving to
darcs2 would help enough.  Here's a summary:

 - using the darcs2 format may well fix the exponential-time merge problem,
  but the UI for merging conflicts is still lacking in many important ways
  in darcs:

  * The conflict markers are not annotated with the patch that they came
    from, and the ordering of patches in conflict markers is
    non-deterministic (when I asked about this problem, I was told it was
    hard to fix).

  * The 'darcs changes' output only shows one of the patches that is
    conflicting, you have to guess at the other one(s).  Also, it doesn't
    show which patches are conflict resolutions.

 - Performance.  darcs2 regressed in performance for many operations we
  commonly use.  I've submitted some measurements for some things, but
  it's pretty easy to find your own test cases: things like "darcs add",
  "darcs whatsnew", "darcs unrecord" are all slower than darcs 1.  When
  simple operations take multiple seconds to complete, it really slows
  down your workflow.

 - I still can't use 'darcs annotate' because it's too slow.  Also, we
  can't browse the GHC repository on the web because the web interface
  wants to do 'darcs changes <file>', and that takes minutes.  It's
  possible with caching, but you still have to regenerate the cache
  after a change.

 - why can I do a complete git clone of a remote GHC repo in a few minutes,
  but it takes hours to do a complete 'darcs get'?

 - Bugs.  Many bugs have been fixed in darcs2, which is great, but we
  did already encounter one (hard to reproduce) bug on Windows,
  when trying to get an up-to-date repo.  Perhaps bugs will be less of
  an issue in the future, but we have had painful experiences
  particularly on Windows and I know the darcs developers are still
  not actively testing on Windows.

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files: unnamed
messages: 5380
nosy: beschmi, dagit, tommy
status: unread
title: Darcs issues with the GHC repository

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