New notes (2011-08)

  • {First,Last}Reverse - newest patches first instead of oldest first
  • Given P and C st C depends on P (ie. P is “Parent”)
  • First (eg. pull): ¬P → ¬C (no to “P” implies no to “C”)
  • FirstReverse (eg. pull –reverse): C → P
  • Last (eg. unpull –reverse): P → C
  • LastReverse (eg. unpull): ¬C → ¬P
  • Watch out for the fact that unpull –reverse is Last, and unpull is LastReverse

Old notes

A large number of darcs commands allow you select a number of patches on which to run some kind of job. How does this patch selection mechanism work?

  • What is reversed for? - this seems to refer to the order in which patches are evaluated. Note that when working with reversed, we also invert the patches
  • What is last for? - this is only used in commands which delete changes or patches (revert, unrecord, obliterate). Note that last does not neccesarily mean that islast will be set! See below.

‘’FIXME: I don’t know what’s going on yet. I’m just taking notes until things become clear for me’’

A job is of type ([Patch],[Patch]) -> IO a. Here is a table of selections of all the jobs which accept input from a selection and meaning of the two patch lists for each job:

|job            | selection  | last/rev     | first     | second  |
|Amend patch    |p from repo |              |oldp       |skipped  |
|Rollback named |ch to file  |last reversed |           |         |
|Rollback prim  |ch to file  |last          |           |         |
|Amend          |ch to file  |              |unrec      |chs      |
|Revert         |ch to file  |last          |p          |skipped  |
|Unrevert       |ch to file  |              |skipped    |p        |
|Record         |ch to file  |              |skipped    |chs      |
|Record deps    |ch          |     reversed |           |deps     |
|Apply          |ch          |              |           |to apply |
|Pull           |ch          |              |           |to pull  |
|Push           |ch          |              |           |to push  |
|Send           |ch          |              |           |to send  |
|Unrecord       |ch          |last reversed |to unrecord|         |
|Obliterate     |ch          |last reversed |ps         |         |

patch selection commands

|text_select |with_any_selected_changes           |
|gui_select  |with_any_selected_changes           |
|text_view   |Changes (with_any_selected_changes) |
|wspr        |with_selected_patch_from_repo       |


  • Useful insight: text_select recursively processes a list of patches, only that we represent this with three lists:

  • lps_done :: [LabelledPatch]

    • patches the user has already looked at
  • lps :: [LabelledPatch]

    • patches which the user has not looked at (head == current patch)
  • pc :: PatchChoices

    • this is where we can look up a patch to see if it should be forced yes or no
  • Before text_select is called - with_any_selected_changes takes care to reverse the patches if isreversed is set. It also does other stuff, but I’m not sure what, yet.

  • isreversed and isinverted are always true at the same time – it’s just that we name them differently to call attention to different aspects of the patch

See also

  • DeveloperFAQ

  • SelectChanges.lhs

    • the user interface to patch selection
  • PatchChoice.lhs

    • the patch selection internals (called by SelectChanges.lhs)