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Overview
We will split current SVN repository located at https://svn.apache.org/repos/asf/sling/trunk/ into multiple git repositories hosted on the ASF git servers. We will opt in to the Git "Dual Master" system which will allow us to push directly to Github. Direct access to Github and the possibility of directly merging pull requests can be a booster for community participation.
We will not enable other Github features, such as wikis, features, and projects.
The rule of the thumb for selecting what ends up in a git repository is a releasable Maven unit. The naming of git repositories will be sling-${sanitizedArtifactId
} . The santizied artifactId is composed from the Maven artifact id where all dots are replaced by slashed. See
Several Apache projects (e.g. ServiceMix, Karaf, Camel) moved from Subversion to Git. Is it time for Sling to move also?
dev@discussions:
- [jira] [Created] (SLING-3987) move from Subversion to Git
- moving sling to git
- [git] Which git system do we want to use?
- [git] Please test sample migrated git projects and repo setup
- [git] Whiteboard migration
See also
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Commit history
Commit history will be preserved as we will convert the projects using git-svn, followed by git filter-branch. However, this has limitations when the project has been moved across multiple directories. We have detected it so far for the repoinit modules. We consider this acceptable, as the full history also resides in SVN. There are no confirmed alternatives that can produce better results. Trying to import the whole ASF SVN repository to experiment with the reposurgeon tool is taking too much time - still not done after five days.
Special situations
The following directories will not be split to individual modules:
- tooling/ide - the modules are not individually buildable and releasable
- performance - the modules are tied together in a performance testing harness
- samples - having samples spread over multiple repositories will make it harder for users to discover all of them
- whiteboard - since we intend to perform no releases from the whiteboard, it does not make sense to create individual repositories. Also, personal Github repositories can be used as well, given that the owner is an Apache committer and only they contribute to that repository.
We will not migrate the attic as there will be no further work done on the modules in there.
The following non-Maven directories will be migrated as separate repositories
- tooling/scm
- tooling/jenkins
Unified view of the repository
We will create the special 'repo' sling which will contain one or more repo
manifests which will allow viewing and editing multiple repositories at once.
Canonical repository URLs
As part of the gitbox setup, the repositories can be accessed both via GitHub and gitbox.apache.org . Since there is a strong requirement to cut releases from ASF servers, all pom references will point to gitbox instead of GitHub. Of course, committers are free to use GitHub as a remote for pushing, just releases are affected.
Migrating a module
If an individual repository needs to be migrated, usually because it was missed from the initial migration, the following steps are needed (assuming we need to migrate contrib/scripting/esx
:
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$ git clone https://github.com/apache/sling-old-svn-mirror # clone the old svn which will be used as a source for the migration
$ cd sling-old-svn-mirror
$ echo contrib/scripting/esx > repo-candidates.txt # file name is not important, but it's helpful to have the name(s) stores in a central place
$ ./tooling/scm/scripts/migrate-to-git.sh -c < repo-candidates.txt # converts the repositories locally in ../sling-modules/
$ ./tooling/scm/scripts/migrate-to-git.sh -r < repo-candidates.txt # provisions the git repository on github/gitbox . Github permissions take 30-60 minutes to sync, you will not be able to push to this repo immediately
$ cp LICENSE ../sling-modules/sling-org-apache-sling-scripting-esx/ && cd ../sling-modules/sling-org-apache-sling-scripting-esx/ && git add LICENSE && git commit -m 'Added LICENSE file' && cd -
$ ./tooling/scm/scripts/migrate-to-git.sh -p < repo-candidates.txt # after verifying that the repository is writable on github
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Once the repository is provisioned add it to the sling-aggregator repo by following the instructions from the aggregator README.
Older information
Tools and scripts
Some WIP tools can be found at https://svn.apache.org/repos/asf/sling/trunk/tooling/scm/scripts/ .
Can Sling (committers and contributors) benefit from moving to Git?
Pros
- offline support
- cherry picking
- easy to move projects (e.g. between bundles, contrib, whiteboard...)
- adpoting the Github workflow using the Git Dual Master system
- ...
...
- not eating our own dog food
- slow for big repositories (many modules)
- tagging is global
- ...
What needs to be prepared for moving to Git?
- repository layout
- release process
- documentation
- CI
- ...
Git at Apache
http://wiki.apache.org/general/GitAtApache
http://www.apache.org/dev/git.html
Repository Layout and Projects (Modules)
There are currently 250 projects (modules) in our repository, counted using the tooling/scm/scripts/gen-repo-candidates.sh
script ( repo-candidates.txt ).
...
Additionally, we will probably have one aggregator repo used to generate the full view over the git repositories, using repo, gitslave, or another tool that we will settle on.
Idea
- one Git repository per project/module (we should keep it that simple - is launchpad really different, a release unit, Justin Edelson?)
- grouping repositories with Google repo, e.g.
core
(bundles
),launchpad
,testing
,samples
,tooling
as needed - using
artifactId
as repository name for artifacts (bundles, plugins, jars, ...) and simple names for grouping (builder/reactor) repositories - using Google repo allows developers to set up their own grouping repositories - even non Sling committers
Grouping repositories (projects/modules)
There are some tools for grouping repositories (projects/modules):
...
- http://blogs.atlassian.com/2013/05/alternatives-to-git-submodule-git-subtree/
- https://codingkilledthecat.wordpress.com/2012/04/28/why-your-company-shouldnt-use-git-submodules/
Pros and Cons
[TODO]
References
dev@discussions:
- [jira] [Created] (SLING-3987) move from Subversion to Git
- moving sling to git
- [git] Which git system do we want to use?
- [git] Please test sample migrated git projects and repo setup
- [git] Whiteboard migration
...