[darcs-devel] adding feature: patch origins

[Sebastian Fischer]

Dear all,

currently `darcs changes` shows information about patches that is
independent of the repository, like its author and creation date,
i.e., when it was recorded.

I would like to add a feature to `darcs changes` to show information
about who added a patch to the current repository (and when it was
added.) This information would typically differ from the currently
shown info if a patch has been recorded in a different repository and
applied to the current repository using a sent patch bundle or by
pushing/pulling from a different repository.

Here is, how it could look like:

    $ darcs changes --last=1 --print-origin
    Sun Feb 10 15:32:44 CET 2013  Sebastian Fischer <sebfisch at example.com>
    pulled: Sun Feb 10 20:32:44 CET 2013  Somebody Else <name at example.com>
      * patch name

      log message given as description of the patch

I looked at the documentation for the new patch index (at
http://darcs.net/Internals/PatchIndex) to see if something like this
can be done with it already, but it does not seem to track the
additional information needed.

I would like to implement origin tracking in a way that does not
influence commands that don't use it. So it seems that other commands
need an option to record the additional information, like

    darcs pull --track-origin

and similar, for push and apply.

It seems that patch origins can be stored in a file patch_origins
similar to how the patch index is stored.

Does this approach sound reasonable? Are there better approaches to
implement this feature? Do you foresee pitfalls that I should avoid?
Would you be willing to incorporate this feature into darcs?

Best,
Sebastian