move to git

[warner]

We've decided to move to git. As #1226 points out, keeping Tahoe in darcs is an unfortunate barrier to entry. This ticket tracks the process.

We'll use the repo that I've been maintaining through a creaky manually-run bidirectional darcs-to-git bridge, and publish on github. I started publishing it under my personal account (and thus it has a few dozen forks), but I created a new "Organization" account and we should publicize that one as the official repo (on github, at least):

​https://github.com/tahoe-lafs/tahoe-lafs

The bridge only handles linear history, so until we drop darcs completely, I'll be rebasing and linearizing everything that touches master. The official repo will only contain a "master" branch, for now: later we'll figure out a release process, and add the 1.8.3 branch back in (which is currently unrepresented in git).

Steps:

• Set up "tahoe-lafs" Github "Organization" account
• Set up post-commit webhook to update tahoe-lafs.org:/home/source/git/tahoe-lafs.git upon changes
• Add "git" repo/branch to Trac
  • this is currently stuck at some old revision: I'm not sure why, maybe some bug in the trac-git plugin
  • turns out the /home/source/webhook daemon needed --umask 002, otherwise when it did a 'git fetch', the new object files were unreadable by the trac daemon
• Set up git-based buildmaster
• Migrate all slaves to the git-based buildmaster
  • create entries for all slaves
  • port all Builders (add buildbot "categories" to mark Builders as "supported", "performance", "packaging", etc, to simplify web display)
  • port the index.html page
  • shut down old buildmaster, change slaveport of new buildmaster to match the old one: boom, all slaves now connect to the new buildmaster
  • get Git installed on all buildslaves that lack it
• update the following wiki pages to instruct people to use git instead of darcs: wiki:NewbieDeveloperSetup, wiki:Dev, wiki:AdvancedInstall (potentially better to remove any instructions on that page about revision control rather than to update the instructions from darcs to git)
• Stop updating darcs repo, freeze it
• Build tool to modify Trac DB [DARCS-REVID] comments to git-based [REVID/git]
• Run revid-mapping tool
• Switch Trac "default branch" to git
• Replace DB comments with [REVID/git] to just [REVID]
• Remove darcs branch from Trac

[warner]

got trac+git fixed, now we see new changes

[zooko]

This will probably fix #1519.

[zooko]

Let's see... Are we waiting for David-Sarah to finish up some darcs branches before we all agree not to push new changes to darcs? Once we've so agreed, I could make the darcs repos read-only in the filesystem.

[zooko]

A next-step here is to write a tool that trawls through the database and replaces [REVNUMBER] with the appropriate git commit id for that darcs commit number, and likewise replaces source:foo@REVNUMBER and (?) I guess also replaces https://tahoe-lafs.org/trac/tahoe-lafs/browser/src/allmydata/web/directory.py?rev=5d404db898e1e6dc#L306 with https://tahoe-lafs.org/trac/tahoe-lafs/browser/src/allmydata/web/directory.py?rev=5d404db898e1e6dc334c3d125ea12a34ea58b13f#L306. Also there may be some darcs patch hash tags, like https://tahoe-lafs.org/trac/tahoe-lafs/browser/src/allmydata/web/directory.py?rev=5d404db898e1e6dc#L306 which should likewise be rewritten.

Actually, since Brian said he wasn't going to do this anytime soon, and I'm not feeling particularly motivated to do it either, maybe a nice interim measure is to just start using src:git/foo instead of src:foo in our *new* comments, and in general to go manually converting such things as are mutable (e.g. wiki pages) to point to https://tahoe-lafs.org/trac/tahoe-lafs/browser/git instead of to https://tahoe-lafs.org/trac/tahoe-lafs/browser/trunk.

[davidsarah]

Why not switch the default trac branch to "git" now? That wouldn't break anything, would it?

[davidsarah]

Replying to davidsarah:

Why not switch the default trac branch to "git" now? That wouldn't break anything, would it?

Oh, of course it would -- it would break all the revision-specific links.