View source for Managing Xen Patches with StGit

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== How To Generate and Submit a Patch to Xen using StGit ==

Xen uses [http://git-scm.com/ Git] for its source code management. The current Xen Project Hypervisor development tree is at http://xenbits.xen.org/gitweb/?p=xen.git;a=summary. Git provides excellent [http://git-scm.com/documentation documentation], please read it if this is your first time using Git. Download and install git to your system. Trees of other teams are listed on [http://xenproject.org/developers/teams.html each teams website] (typically in a highlighted box on the right of each page called ''<Project Name> Resources'' or ''<Project Name> Code'') or our [http://xenbits.xen.org/gitweb/ gitweb instance].

=== Recommended git extensions ===

To be able to manage patches better I recommend [http://www.procode.org/stgit/ StGit], which is an application that runs on top of git and provides a functionality similar to Mercurial PatchQueue extension. This tutorial will show how to manage branches with git and StGit, so before proceeding please make sure that StGit is installed.

=== Generating a patch ===
----
Here's a recommendation on how to send patches, as suggested by the Xen maintainers.

The first thing to do is cloning the xen git repository:

<pre>
git clone git://xenbits.xen.org/xen.git
</pre>

This will create a new folder, called xen, where you will work on your patches. We are going to create a branch for each series of patches that we are going to work on. This will allow a developer to work on several patch series at the same time, keeping the patches contained and well classified. Now we will create a new branch on top of the default branch, which is called "master".

<pre>
stg branch -c my_new_feature
</pre>

You are now working on a different branch, you can switch back to the "master" branch at any time by using:

<pre>
stg branch master
</pre>

Now that we are on the branch we wish to use to develop feature X we will start creating patches. The first thing to do is creating a new patch, StGit will ask for a description of the patch, but if unsure you can leave it blank and fill it later.

<pre>
stg new first_patch_in_the_series
</pre>

Here is an example of a simple description:

<pre>
foobar: Add a new trondle calls

Add a some new trondle calls to the foobar interface to support
the new zot feature.

Signed-off-by: Joe Smith <joe.smith@citrix.com>
</pre>

The first line in the description will be used as the subject when the patch is sent to the mailing list, so please make sure it contains an accurate description about what the patch is expected to introduce. It should be followed by a more accurate description and finally a "Signed-off-by".

Now you can starting modifying the code, all your changes will be contained inside this patch. When finished, you will have to refresh the patch, and create a new one on top if desired.

<pre>
stg refresh
stg new second_patch_in_the_series
</pre>

If you want to modify the description of a patch, you should use the [http://procode.org/stgit/doc/stg-edit.html edit] command:

<pre>
stg edit first_patch_in_the_series
</pre>

Also, if you want to move between the series, you can use the following StGit commands, [http://procode.org/stgit/doc/stg-push.html push], [http://procode.org/stgit/doc/stg-pop.html pop] and [http://procode.org/stgit/doc/stg-goto.html goto].

=== Sending a patch to xen-devel@ ===
You can find instructions on how to send patches in our [[Submitting_Xen_Project_Patches#send|Patch Submission Guide]].

=== Common tasks ===
----
If you are working on a big or controversial patch series, it is very likely that you will have to submit several versions of them, and you will need to rebase your code to match the changes that will be committed to the repository  between each revision of your series. You can do that easily with [http://www.procode.org/stgit/doc/stg-rebase.html stg rebase]. The first step is to update the "master" branch of your repository.

<pre>
stg branch master
git pull
</pre>

After that you will need to find the commit ID you want to rebase your series on top of, this can be done using git log. Once you have the commit ID, switch to the branch with your patches and execute:

<pre>
stg rebase <commit-id>
</pre>

This will pop all your patches, move the branch to the commit specified and then push your patches again. There's a chance that your patches don't apply cleanly on top of this commit, if this is the case stg will complain loudly, and you will have to manually edit the conflicting file. After editing the file, you can add it to your repository again and continue with the rebase:

<pre>
git add <conflicting/file>
stg refresh
stg push
</pre>

stg rebase is really useful, because it allows you to rebase your series on top of any commit, as an example, you can rebase one of your series on top of another, or rebase a series on top of staging changes.

== StGit Tutorials ==
* [https://events.linuxfoundation.org/sites/events/files/slides/An%20Introduction%20to%20Stacked%20Git.pdf An introduction to Stacked Git]
* [http://procode.org/stgit/doc/tutorial.html StGit Tutorial]

[[Category:Developers]]
[[Category:Development Process]]
[[Category:Xen]]