Revision as of 11:17, 5 August 2011

We'd like to capture some common CVS workflows used by the Eclipse Project and spell out the git/EGit equivalent.

Please read some of Pro Git to get a feel for how git repositories work. Refer to the EGit/User Guide for more detailed instructions and pictures.

Getting EGit

You can install EGit 1.0.0 from Indigo, it's already available.

If you would like to keep up with their current bug fixes, install EGit/JGit from their nightly build site http://download.eclipse.org/egit/updates-nightly. You might have to use the site suggested in bug 331301- Updating from nightly build fails with MD5 error until that bug is fixed.

Clone a repo

The first step is to clone the one or more repos you need to work on. You want to clone the repo to a location outside your workspace. Then use the EGit Import Projects option to import the projects.

Refer to the EGit/User Guide for more detailed instructions and pictures.

1. Switch to the Git Repository Exploring Perspective
2. Use Clone a Git repository
3. you can paste in your connection URL and it should do the right thing. Some URLs (not all of them contain content right now in the testing phase), Those repos that have been migrated are bolded:
   1. ssh://userid@git.eclipse.org/gitroot/equinox/rt.equinox.bundles.git
   2. ssh://userid@git.eclipse.org/gitroot/equinox/rt.equinox.binaries.git
   3. ssh://userid@git.eclipse.org/gitroot/equinox/rt.equinox.framework.git
   4. ssh://userid@git.eclipse.org/gitroot/equinox/rt.equinox.incubator.git
   5. ssh://userid@git.eclipse.org/gitroot/equinox/rt.equinox.p2.git
   6. ssh://userid@git.eclipse.org/gitroot/equinox/rt.equinox.security.git
   7. ssh://userid@git.eclipse.org/gitroot/jdt/eclipse.jdt.core.git
   8. ssh://userid@git.eclipse.org/gitroot/jdt/eclipse.jdt.debug.git
   9. ssh://userid@git.eclipse.org/gitroot/jdt/eclipse.jdt.git
   10. ssh://userid@git.eclipse.org/gitroot/jdt/eclipse.jdt.ui.git
   11. ssh://userid@git.eclipse.org/gitroot/pde/eclipse.pde.build.git
   12. ssh://userid@git.eclipse.org/gitroot/pde/eclipse.pde.git
   13. ssh://userid@git.eclipse.org/gitroot/pde/eclipse.pde.incubator.git
   14. ssh://userid@git.eclipse.org/gitroot/pde/eclipse.pde.ui.git
   15. ssh://userid@git.eclipse.org/gitroot/platform/eclipse.platform.debug.git
   16. ssh://userid@git.eclipse.org/gitroot/platform/eclipse.platform.git
   17. ssh://userid@git.eclipse.org/gitroot/platform/eclipse.platform.releng.git
   18. ssh://userid@git.eclipse.org/gitroot/platform/eclipse.platform.resources.git
   19. ssh://userid@git.eclipse.org/gitroot/platform/eclipse.platform.runtime.git
   20. ssh://userid@git.eclipse.org/gitroot/platform/eclipse.platform.team.git
   21. ssh://userid@git.eclipse.org/gitroot/platform/eclipse.platform.text.git
   22. ssh://userid@git.eclipse.org/gitroot/platform/eclipse.platform.ua.git
   23. ssh://userid@git.eclipse.org/gitroot/platform/eclipse.platform.ui.git 
   24. ssh://userid@git.eclipse.org/gitroot/platform/eclipse.platform.swt.git 
   25. ssh://userid@git.eclipse.org/gitroot/platform/eclipse.platform.swt.binaries.git
4. Next
5. Select all branches to clone
6. Next
7. Confirm the location that it will clone the repository into.
8. an initial branch of master and a remote name of origin are standard.
9. Finish - Now just sit back while git copies the entire repo to your harddrive :-)

Configuring the repo

Unless you are working on topic branches, we work in a fairly linear history. Please set branch.branchname.rebase = true.

Once you've cloned a repository, you can go the the Preferences>Team>Git>Configuration page. Select your repository, select the branch you picked when you cloned the repo, and add the new entry. Ex, for the default clone of master, use branch.master.rebase=true

Importing the projects

We need to get the projects from the repo into our workspace:

1. right click on your newly cloned repo and select Import Projects
2. you want Import existing projects from the Working Directory
3. Next
4. Select the projects that you want to import from the repository
5. Finish

Now you can start working.

A note on deleting projects

Typically you will only want to have a subset of the projects from a given repository in your workspace. When you are no longer interested in a project, you can delete it from your workspace. However, NEVER select 'Delete project contents on disk' for a project in a git repository. If you do, Git will consider this an outgoing deletion to be committed to the remote branch. Later while working on a completely unrelated project you may accidentally commit this deletion (and you wouldn't be the first to do so).

Start working in HEAD

To start working in HEAD you must clone your repository and checkout a working copy. By default, cloning the repo checks out the master branch, which is the same as HEAD in CVS.

See #Clone_a_repo.

Refer to the EGit/User Guide for more detailed instructions and pictures.

The constant HEAD is used in GIT as well, but has a completely different meaning. In GIT HEAD means the pointer to the latest commit in your currently checked-out branch (more or less).

Start working in a new branch

For example, create the R3_7_maintenance branch for your repo. This example is for the case that your branch doesn't already exist as refs/remotes/origin/R3_7_maintenance.

Refer to the EGit/User Guide for more detailed instructions and pictures.

1. right click on one of your projects and choose Team>Switch To>New Branch
2. you need to pick a source ref.
   1. HEAD == current checked out commit
   2. refs/heads/master means your master branch.
   3. refs/remotes/origin/R3_7_maintenance - the existing remote branch. If you pick this one and name your local branch the same, EGit will automatically create a tracked branch.
   4. refs/tags/R3_7 is the tags to branch from
3. name the branch R3_7_maintenance
4. select the Rebase merge option
5. leave "Check out the new branch" selected.

This will create a new branch for you to work on. Once you've made your initial commits, you need #Commit_changes_to_the_main_repo. Pushing up to the repo will push any new branches you've created as well.

Create a patch

We have 2 options for accepting contributions from the community. See Development Resources/Handling Git Contributions (prefered) and Git#IP_process_implications_of_DVCS. Refer to the EGit/User Guide for more detailed instructions and pictures.

To create a patch:

1. You need to show the commits in the history view.
   1. Either right-click on a file you just committed and Show in history
   2. or right-click on the project and Show In>History, then find the commit you want
2. right click on the commit in the History view, and select Create Patch
3. use Next if you'd like the patch in the standard git mbox format

Apply a patch

A normal workspace patch will apply in the same fashion it does for CVS. Simply copy the file to the clipboard and paste it into the Package Explorer or use Team>Apply Patch.

Refer to the EGit/User Guide for more detailed instructions and pictures.

Patches created with git/EGit have a different pattern. They are diff statements that look like:

 diff --git a/bundles/org.eclipse.e4.ui.workbench.renderers.swt/src/org/eclipse/e4/ui/workbench/renderers/swt/HandledContributionItem.java b/bundles/org.eclipse.e4.ui.workbench.renderers.swt/src/org/eclipse/e4/ui/workbench/renderers/swt/HandledContributionItem.java
index 99d339f..37bcf68 100644
--- a/bundles/org.eclipse.e4.ui.workbench.renderers.swt/src/org/eclipse/e4/ui/workbench/renderers/swt/HandledContributionItem.java
+++ b/bundles/org.eclipse.e4.ui.workbench.renderers.swt/src/org/eclipse/e4/ui/workbench/renderers/swt/HandledContributionItem.java

To apply a patch like this, you should:

1. copy and paste the patch into the Package Explorer
2. Select Apply patch to the workspace root
3. Next
4. under Patch Options set Ignore leading path name segments to 2
5. now you can examine the patch and apply is normally.

Tag the mapfile for a build

We're still deciding on a best practice on tagging the repos and updating the map files for an I build.

One option under discussion is to allow the I build to tag the repos and update the map files automatically based on master. In the normal case, the build will run with master. If we need a fix, a map file can be reverted and a new I build with "no repo tagging" can be started.

When we have a bug for the discussion I'll update this item with the number.

Commit changes to the main repo

Committing a change to the main repo is a 2-step process in git. In git, a commit creates a commit with the changed files in your local clone repository. A push will put that commit in our main repo. Committing and pushing are distinct operations in git.

Refer to the EGit/User Guide for more detailed instructions and pictures.

To get your changes to the main repo in EGit:

1. Do a pull or a fetch and a merge into your working branch
2. right-click on your project and use Team>Commit
3. Your commit message should include the bug number you are using for your fix/work.
4. check the files that should be included in the commit in the Files section
5. Commit

Then you need to push your changes to make sure they've visible to everyone else

1. right-click on your project and use Team>Push to Upstream
2. it should provide a status dialog with the refs that were updated, or a failure if the main repo has commits that you haven't either merged or rebased on.
3. if there's a failure, you need to #Update_to_pull_in_the_latest_changes_to_HEAD or the relevant branch.

Common commit message:

 Bug 349177 - [releng] stitch ui.workbench fork back into main
Updating some code to reflect the real change

Update to pull in the latest changes to HEAD

To make changes visible from our main repo is a 2 step process in git:

1. fetch which updates your cloned repo with all of the objects and remote branches from the main repo.
2. merge which updates your local branch to point to the correct commit
   1. the most common case is called the "fast forward merge". That's where your repo has no local changes, and git can simply update your local master to the commit pointed to by origin/master
   2. if you have a local commit that has not yet been pushed, you might have to deal with merge conflicts:
      1. you will either have to merge the new origin/master into your master (which will lead to a merge commit with 2 parent commits)
      2. or rebase your local commit onto that last commit coming from origin/master. This leaves the history of the main repo as a simple line, and is prefered ... I think.

Refer to the EGit/User Guide for more detailed instructions and pictures.

Git can do both fetch and merge for the current branch at once:

1. right click on your project and select Team>Pull

Merge conflicting changes

Refer to the EGit/User Guide for more detailed instructions and pictures.

If you pull changes for your branch and there are conflicts, you must merge them before you can commit your changes.

By default EGit merges conflicts into the local files using the old merge syntax Text Merge Markers. To switch to a compare editor merge, use the Team>Merge Tool menu item. See EGit/User Guide#Resolving_a_merge_conflict

Cross-referencing between bugzilla and git

Some committers like to attach patches to bugzilla for all changes, so they have a record of exactly what changes occurred to fix the bug. With git there is a better way:

• Push the change to git.eclipse.org
• Navigate to git.eclipse.org in your web browser
• Find your repository, and click on the "Log" tab
• Click on your commit, which should be near the top of the log at this point
• You are now on a page that shows a graphical diff of call changes that occurred in that commit. Copy the URL of this commit page into a bugzilla comment.

Now if someone in the future wants to see what changes were made to fix the bug, they have a one click link to see all the changes.

References

• EGit/User Guide - describes the dialogs and commands that can be accessed for the EGit eclipse plugin
• Pro Git - a handy description of how git works and some of what git can do
• Git SCM - the main git site
• msysgit - A git client and bash shell for windows - might need some crlf flags set, not sure.