ryppl / subconvert Goto Github PK

Faithfully convert Subversion repositories to Git.

SubConvert.py, version 1.0
 
Copyright (c) 2011, BoostPro Computing.  All rights reserved.

This script replays Subversion dump files as Git actions, yielding a Git
repository which has as close of a 1:1 correspondence with the original
Subversion repository as possible.

Some respects in which this are not possible are:

* Subversion allows for multiple transactions within a single revision, and it
  is possible that some of those transactions may affect more than one branch.
  This must be mapped as two separate Git commits if/when it occurs.

* Subversion supports revisions which modify only directories and/or
  properties of files and directories.  Since Git tracks only files, and has
  no notion of Subversion's properties, these revisions are ignored.

* Subversion models all content in a flat filesystem, such that semantically,
  there is no distinction between branches and tags, except that typically a
  "tag" is a directory which is never modified after initial creation.

  Because proper identification of branches and tags cannot faithfully be done
  hueristically, this script makes a best guess based on activity within all
  revisions, and then outputs a data file for the user to correct before
  performing the final conversion.

* Subversion also tracks version history for multiple projects within this
  same, single filesystem.  This script, if provided with a submodules
  "manifest" file, can create multiple repositories in parallel: one to model
  the original Subversion repository as exactly as possible, with all projects
  conflated in a single filesystem; and a separate repository for each
  submodule.

Note that for efficiency's sake -- to avoid thrashing disk unnecessarily and
taking orders of magnitude more time -- this script performs Git actions
directly, completely bypassing use of a working tree.  That is, instead of
using porcelain commands such as git add, remove, commit, etc., and git
checkout to switch between branches, it uses the underlying plumbing commands:
hash-object, mktree, commit-tree, update-ref, symbolic-ref, etc.  The final
checkout to yield the working tree(s) is done only after all repositories and
their branches and tags have been finalized.