Talk I presented at the BigCommerce meetup recently

1. SVN to Git Migration

2. Technology
➔
Gitolite.
➔
Atlassian Suite.
➔
Internal system ”Octopus”.

3. Migrating
the code

4. git-svn
➔
Slow...
➔
Didn't handle shallow merges well.
➔
Our old branches didn't map well.
➔
Works fine for small repos.
➔
Not right for our repo.

5. svn-all-fast-export
➔
Faster.
➔
Direct access to git from C libs.
➔
Easier to configure.

6. svn-all-fast-export
# rules­map
create repository bigcommerce
end repository
match /trunk/
repository bigcommerce
branch master
end match
...
match /branches/([^/]+)/
repository bigcommerce
branch 1
end match
...
match /tags/7.3.23/
repository bigcommerce
branch refs/tags/7.3.23
annotated true
end match

7. svn-all-fast-export
# svn­authors
anna.pomroy = Anna Pomroy <anna.pomroy@bigcommerce.com>
chris.beckett = Chris Beckett <chris.beckett@bigcommerce.com>
chris.boulton = Chris Boulton <chris.boulton@bigcommerce.com>
...
# import command
svn­all­fast­export ­­identity­map svn­authors ­­rules
map ­­add­metadata /var/svn/bigcommerce

8. svn-all-fast-export
➔
Problem:

Post migration branch amnesia.

Only affected some branches.
➔
Solution(s):

Patch from the original svn branch.

Rebranch in git, resolve lots of conflicts and
pay close attention!

9. svn-all-fast-export
➔
Problem:

Wrong revision used to create a branch on
import.
➔
Solution:

Fix it in the source & submit a patch!

Check & double check...

10. How are we
using git?

11. SVN branching model
Tues Mon Tues Mon
Stability
Feature-Y
Feature-X
Trunk
RC-02
x
RC-01
tfi
Ho
1.0 1.2
Time

12. Gitflow branching model
Tues Mon Tues Mon
Stability
Feature/y
Feature/x
Develop
Release/1.0 Release/1.3
master 1.3
1.0 1.2 1.3
Time

13. Rome wasn't
built in a day...

14. Identified issues
➔
svn:ignore.

Create .gitignore
➔
Empty directories.

Fill with .empty files
➔
Commit hooks.

Use gitty for hook management.

15. Unidentified problems
➔
”Time & tide waits for no man”.

We were fixing the deployment system
”Octopus” on the day.

Last minute cherry-picks to tags/branches to
get them working.

16. Why did we do it?
”...what if anything is
”I miss my git blocking us from
switching to git for
staging area already” source control?”
”Maybe we should ”f**k; I keep
evaluate git more” typing git status”

17. Immediate Benefits
➔
Decentralised, remote work.
➔
Much, much faster.
➔
Staged commits, stashes.
➔
Flexible & powerful cmd line.

18. Questions?