Internals/Record

Purpose

The purpose of this document is to explain in low level and concrete terms how the command ‘darcs record’ works. This is description is intended to give enough details that a programmer new to darcs could implement their own ‘darcs record’. We focus on darcs-2 format repositories.

Steps

  1. Take the repository lock (withRepoLock)
  2. Read the recorded repository (slurp_recorded)

    1. Read _darcs/hashed_inventory
    2. Construct in-memory representation of pristine (eg., Slurpy)
  3. Sort file names in pristine
  4. Construct patches from recorded state (pristine) to state of working dir. These are the unrecorded changes (unrecordedChanges).

    1. read pending patches from _darcs/patches/pending, as a sequence of primitive patches
    2. read recorded state of pristine as a Tree (hashed-storage)
    3. check that pending applies cleanly to recorded state
    4. read pending patches again
    5. look through working directory (and Tree index) to find unrecorded changes, ignoring boring files
  5. Ask user which patches to record (with_selected_changes_to_files’)
  6. Record selected patches (do_actual_record)

    1. create patch from name and sequence of prim patches
    2. add to inventory (tentativelyAddPatch)

      1. Generate a hash for the patch
      2. Add the patch info and hash to _darcs/tentative_hashed_inventory
      3. Write the patch to the cache (hash collisions are treated as the patch already existing)
    3. invalidate hashed-storage index (invalidateIndex)
    4. finalize changes (withGutsOf/finalizeRepositoryChanges)

      1. Test tentative
      2. Block signals
      3. finalize_tentative_changes ~ 1. optimize inventory: ~ 1. read_tentative_repo 2. write_tentative_repo

        2.  Read \_darcs/tentative\_hashed\_inventory
        3.  Read \_darcs/tentative\_pristine
        4.  TODO: document inv2pris/pris2inv and invisiblePS
    5. delete log file