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Google Code -> GitHub

Saturday, 03 March 2012

Herein a walk-through of moving a project from Google Code to GitHub. The project is “python-markdown2”: on Google Code -> on GitHub. It was single-commiter subversion project on Google Code with one tag and no branches. It had (has) a number of issues in the issue tracker, a few wiki pages and a few downloads.

This includes a couple tools I wrote for converting between Google Code and GitHub project wikis and issue trackers. Note: I originally did this migration almost a year ago, so I’m not positive whether recent changes in the GitHub issues API might break this tool.

github project

First create the new project on GitHub.

source code repo

As per http://help.github.com/svn-importing/, svn2git is preferred. At first I hit an inscrutable error from ‘svn2git’:

error: pathspec 'master' did not match any file(s) known to git

The only reference I could find with a cure was:


which indicated that you need an entry in “authors.txt” for “(no author)”, something like so:

(no author) = unknown author <unknown@example.com>

My first import attempt appeared to work, but failed to import all commits. A subsequent attempt (this time with “–verbose” option) worked. Not sure if “–verbose” makes a difference. I hope not. Here were my steps:

$ cat ~/tm/authors.txt
trentm = Trent Mick <trentm@gmail.com>
(no author) = unknown author <unknown@example.com>
$ mkdir ~/tm/python-markdown2
$ cd ~/tm/python-markdown2
$ svn2git https://python-markdown2.googlecode.com/svn --authors ~/tm/authors.txt
W: -empty_dir: trunk/test/tm-cases/blog.markdown
W: -empty_dir: trunk/test/tm-cases/extintro.markdown
W: -empty_dir: trunk/test/tm-cases/link_defn_alt_title_delims.tags
W: -empty_dir: trunk/test/tm-cases/safe_mode.html
W: -empty_dir: trunk/test/tm-cases/safe_mode.opts
W: -empty_dir: trunk/test/tm-cases/safe_mode.text
W: -empty_dir: trunk/markdown2.py
W: -empty_dir: trunk/bin/markdown2
W: -empty_dir: trunk/test/tm-cases/issue31_gt_escaping.html
W: -empty_dir: trunk/test/tm-cases/issue31_gt_escaping.tags
W: -empty_dir: trunk/test/tm-cases/issue31_gt_escaping.text
Found possible branch point: https://python-markdown2.googlecode.com/svn/trunk => https://python-markdown2.googlecode.com/svn/tags/v1.0.1.17, 240
Use of uninitialized value $u in substitution (s///) at /usr/local/git/libexec/git-core/git-svn line 1731.
Use of uninitialized value $u in concatenation (.) or string at /usr/local/git/libexec/git-core/git-svn line 1731.
refs/remotes/trunk: 'https://python-markdown2.googlecode.com/svn' not found in ''

Note: checking out 'trunk'.

You are in 'detached HEAD' state. You can look around, make experimental
changes and commit them, and you can discard any commits you make in this
state without impacting any branches by performing another checkout.

If you want to create a new branch to retain commits you create, you may
do so (now or later) by using -b with the checkout command again. Example:

  git checkout -b new_branch_name

HEAD is now at acb4fca... TODOne a while back
error: branch 'master' not found.
Switched to a new branch 'master'
Counting objects: 1175, done.
Delta compression using up to 4 threads.
Compressing objects: 100% (1069/1069), done.
Writing objects: 100% (1175/1175), done.
Total 1175 (delta 611), reused 0 (delta 0)
Removing duplicate objects: 100% (256/256), done.

HEAD is now at cb87cf8... Tweaks to 'header-ids' and 'toc' extras. Also add a ".postprocess(text)" hook for subclasses' convenience.
Running command: git branch -D master
Deleted branch master (was cb87cf8).
Running command: git checkout -f -b master
Switched to a new branch 'master'
Running command: git gc
Counting objects: 1290, done.
Delta compression using up to 4 threads.
Compressing objects: 100% (1166/1166), done.
Writing objects: 100% (1290/1290), done.
Total 1290 (delta 681), reused 0 (delta 0)
Removing duplicate objects: 100% (256/256), done.

Then a sanity check diffing the HEAD state in an svn working copy and a git clone:

$ diff -ru -x .svn -x .git python-markdown2.svn python-markdown2 | less
diff -ru -x .svn -x .git python-markdown2.svn/externals/which/which.py python-markdown2/externals/which/which.py
--- python-markdown2.svn/externals/which/which.py       2010-10-14 09:55:52.000000000 -0700
+++ python-markdown2/externals/which/which.py   2011-01-31 21:14:20.000000000 -0800
@@ -65,7 +65,7 @@
     files without executable access.

-__revision__ = "$Id: which.py 82 2007-11-06 05:44:22Z trentm $"
+__revision__ = "$Id$"
 __version_info__ = (1, 1, 3)
 __version__ = '.'.join(map(str, __version_info__))
 __all__ = ["which", "whichall", "whichgen", "WhichError"]

That’s an acceptable diff. I don’t care about that “$Id$” expansion facility.

Now for ignore-patterns:

$ cd python-markdown2
$ svn propget svn:ignore ../python-markdown2.svn > .gitignore
$ git add .gitignore
$ git commit -m ".gitignore from svn:ignore" .gitignore
[master d31e29e] .gitignore from svn:ignore
 1 files changed, 8 insertions(+), 0 deletions(-)
 create mode 100644 .gitignore

In general you’d have to walk the full svn working copy for ‘svn:ignore’ properties on any directory. In my case I had a bunch to incorporate (manually) into my “.gitignore” file:

$ find . -type d | grep -v .svn | xargs svn pl -v .
Properties on '.':

Properties on 'externals':

Properties on 'externals/which':

Properties on 'lib':

Properties on 'perf':

Properties on 'sandbox':

Properties on 'test':

Time to push this to github:

cd .../python-markdown2
git remote add origin git@github.com:trentm/python-markdown2.git
git push origin master

Google Code project page -> README.md

A Google Code project’s front page is the wiki-formatted project page. A GitHub project’s front page (prose) is the README file. You might want to start with your Google Code project wiki page content (at http://code.google.com/p/PROJNAME/admin) and use that to create a README.md (or README.txt or whatever). I already had a README.txt and I’m a Markdown guy (duh) so I converted it to README.md to have it rendered nicely on my GitHub project page.

wiki pages

Google Code for a long time (from the get go?) allowed you to have a wiki for your project whose content is in Subversion – nice feature. GitHub more recently added support for project wiki pages being in a git repo. This will make moving wiki pages straightforward.

First, create your wiki on GitHub by clicking “Create Wiki Now” on https://github.com/USERNAME/PROJNAME/wiki. Then let’s get working copies of the old and the new:

cd ...
svn co https://python-markdown2.googlecode.com/svn/wiki python-markdown2-wiki.svn
git clone git@github.com:trentm/python-markdown2.wiki.git

At this point you could do a whole subversion history conversion to git, but I don’t care about the wiki editing history.

Let’s just copy over and convert the files.

python googlecode2github/wikiconvert.py \
    trentm/python-markdown2 \
    python-markdown2-wiki.svn \

“wikiconvert.py” is a tool I wrote to help with this conversion. It doesn’t cover the full Google Code wiki syntax, just enough for what was my typical usage… so you may want to do some post tweaking. However, it should be a good start. See https://github.com/github/gollum for details on other wiki tweaks you can do on GitHub. “wikiconvert” lives here https://github.com/trentm/googlecode2github.

Review, commit and push in ‘python-markdown2.wiki’:

cd python-markdown2.wiki
git add .
git diff --staged
git commit -m "convert wiki from code.google.com/python-markdown2 with 'googlecode2github/wikiconvert'"


Fully transplanting all issues (along with timing, status, user data, comments, attachments, etc.) is a fool’s errand. Instead we’ll just create a shadow issue for each google code issue so that (a) we have a pointer for all issues from the new GitHub project and (b) there are no issue number collisions when new issues are added on GitHub.

“googlecode2github/shadowissues.py” (see https://github.com/trentm/googlecode2github) will do this for us. For each shadow issue it’ll try to reproduce the title, original description and the closed/open state. To make changes you GH issues, the script will need you github username and API token. The latter is available at https://github.com/account#admin_bucket. The script will ask interactively or you can add them to your “~/.gitconfig” via:

git config --add github.user [github_username]
git config --add github.token [github_api_token]

As a sanity check, I suggest that you first run this against a test github project (e.g. I used “trentm/ghtest”). This is because “shadowissues.py” wants the shadow issues to have the issue ids match those in the Google Code project. You cannot delete issues on a github project (a good thing) so you only get one chance:

$ python .../googlecode2github/shadowissues.py python-markdown2 trentm/ghtest
# Gathering code.google.com/p/python-markdown2 issues.
# Gathering any github.com/trentm/ghtest issues.
Migrating issue 1.
 from: http://code.google.com/p/python-markdown2/issues/detail?id=1
   to: https://github.com/trentm/ghtest/issues/1

Review those created GH-issues, then if things look good, run it for realz:

$ python .../googlecode2github/shadowissues.py python-markdown2 trentm/python-markdown2
# Gathering code.google.com/p/python-markdown2 issues.
# Gathering any github.com/trentm/python-markdown2 issues.
Migrating issue 1.
 from: http://code.google.com/p/python-markdown2/issues/detail?id=1
   to: https://github.com/trentm/python-markdown2/issues/1

One last change for issues: Now that you’ve moved to github, you want new issues to be added there. You might want to change the Google Code new issue template to something like this:

NOTICE: This project has moved to <https://github.com/trentm/python-markdown2>.
Please report your issue here:


This can be done on the equivalent of http://code.google.com/p/python-markdown2/adminIssues for your project.

pointer from google code to github

A few extra touches for your Google Code project to provide pointers to the new GitHub location.

  • Summary: append ` (MOVED TO GITHUB)`
  • Description: prepend = Note: This project has been moved to [https://github.com/trentm/python-markdown2 trentm/python-markdown2 on GitHub]. =
  • Wiki pages: prepend = Note: This project has been moved to [https://github.com/trentm/python-markdown2 trentm/python-markdown2 on GitHub]. =