reposurgeon 2.0 announcement – the full-orchestra version

I shipped reposurgeon 2.0 a few days ago with the Subversion support feature-complete, and a 2.1 minor bugfix release this morning. My previous release announcement was somewhat rushed, so here is a more detailed one explaining why anybody contemplating moving up from Subversion should care.

To go with this, there is a new version of my DVCS Migration HOWTO.

reposurgeon can now read and analyze Subversion stream dumps, and can translate them to git fast-import streams. This brings with it the ability to export not just to git but to any DVCS that can speak that stream format; reposurgeon currently has direct support for hg and bzr.

Branchy repos are automatically handled correctly, with trunk mapped to master and Subversion branches maped to gitspace branches.
Subversion tags are automatically mapped to git annotated tags (or to branches with tagged ends if the tag directory was modified after the copy).
Multibranch commits are automatically split into annotated per-branch commits.
Various kinds of meaningless cruft and artifacts generated by older versions of cvs2svn are automatically cleaned up. (But no potentially interesting comments or metadata are ever thrown away.)
Ersatz branch copies consisting of a plain directory copy followed by multiple adds are detected and treated like intentional branch creations.
svn:ignore property settings and clears are automatically translated to equivalent creations and removals of .gitignore files.
There is semi-automated support for lifting CVS and Subversion commit references in change comments to a VCS-independent date!committer format.
svn:special properties are translated to git symlink references.
It is never necessary to hint to reposurgeon or give it branch-rewrite rules to get a clean lift. In some very unusual theoretical cases, post-lift surgery to sort out branches might be required, but no example of this has yet been observed in the wild.
What reposurgeon does is carefully and exhaustively documented, even in the strange edge cases.

Most of the pre-existing conversion tools don’t do any of these things properly. reposurgeon does them all, with an extensive regression-test suite to demonstrate correctness. The code has also been field-tested on several large Subversion repositories (notably for the gpsd, Hercules, NUT, and Roundup projects) with good results.

I believe reposurgeon now does almost as good a job of lifting as is possible given the ontological differences between Subversion and git. I say “almost” only because there is still some room for improvement in recognizing Subversion branch-merges-by-copy and translating them as gitspace DAG merges.

Note one important restriction: reposurgeon can read Subversion dumps, but cannot write them – the downconversion from fast-import streams would be too lossy to be safe.

I started working on the Subversion-stream support about a year ago. What took so long was getting the multibranch support to automatically do the right thing in various semi-pathological merge cases.

Fear the reposturgeon!