ITK/Git/Develop

This page documents how to develop ITK through Git. See our table of contents for more information.

Git is an extremely powerful version control tool that supports many different "workflows" for indivudal development and collaboration. Here we document procedures used by the ITK development community. In the interest of simplicity and brevity we do not provide an explanation of why we use this approach. Furthermore, this is not a Git tutorial. Please see our Git resource links for third-party documentation, such as the ProGit Book.

Setup

Before you begin, perform initial setup:

1. Register Gerrit access and possibly Git push access.
2. Optionally download our one page PDF desk reference.
3. Follow the download instructions to create a local ITK clone:
$ git clone git://itk.org/ITK.git	Connection refused?
4. Run the developer setup script to prepare your ITK work tree and create Git command aliases used below:
$ ./Utilities/SetupForDevelopment.sh	SetupForDevelopment.sh Pro Git: Setup

Note that if you answer 'y' to the question "Do you want to test push access to itk.org? [y/N]:", you will most likely receive the following error message: "Permission denied (publickey). fatal: Could not read from remote repository.". Only a few experienced contributors have push access. Having push access is not necessary to contribute to ITK.

Workflow

ITK development uses a branchy workflow based on topic branches. Our collaboration workflow consists of three main steps:

1. Local Development
Update
Create a Topic
2. Code Review
Share a Topic (requires Gerrit access)	Gerrit Code Review
Revise a Topic
3. Integrate Changes
Merge a Topic (requires Git push access)
Delete a Topic

Update

Update your local master branch:
$ git checkout master $ git pullall	git help checkout alias.pullall (pull and submodule update)

Create a Topic

All new work must be committed on topic branches. Name topics like you might name functions: concise but precise. A reader should have a general idea of the feature or fix to be developed given just the branch name.

To start a new topic branch:
$ git fetch origin For new development, start the topic from origin/master: $ git checkout -b my-topic origin/master For release branch fixes, start the topic from origin/release, and by convention use a topic name starting in "release-": $ git checkout -b my-topic origin/release	git help fetch git help checkout git help submodule Pro Git: Basic Branching
Edit files and create commits (repeat as needed). Add a prefix to your commit message (see below).
$ edit file1 file2 file3 (To add data follow these instructions.) $ git add file1 file2 file3 $ git commit	git help add git help commit Pro Git: Recording Changes
(If your change modifies the "Modules/ThirdParty/KWSys/src/KWSys" directory please contribute directly to KWSys instead.) (If your change modifies the "Modules/ThirdParty/MetaIO/src/MetaIO" directory please contribute directly to MetaIO instead.)
Standard prefixes for ITK commit messages : BUG: Fix for runtime crash or incorrect result COMP: Compiler error or warning fix DOC: Documentation change ENH: New functionality PERF: Performance improvement STYLE: No logic impact (indentation, comments) WIP: Work In Progress not ready for merge

Share a Topic

When a topic is ready for review and possible inclusion, share it by pushing to Gerrit. Be sure you have registered for Gerrit access.

Checkout the topic if it is not your current branch:
$ git checkout my-topic	git help checkout
Check what commits will be pushed to Gerrit for review:
$ git prepush	alias.prepush (log origin/master..)
Push commits in your topic branch for review by the community:
$ git gerrit-push (If the topic adds data see this note.) or if you started the topic from the release branch: $ git push gerrit HEAD:refs/for/release/my-topic	Connection refused? alias.gerrit-push (Utilities/Git/git-gerrit-push)

Find your change in the ITK Gerrit instance and add reviewers.

Revise a Topic

If a topic is approved during Gerrit review, skip to the next step. Otherwise, revise the topic and push it back to Gerrit for another review.

Checkout the topic if it is not your current branch:
$ git checkout my-topic	git help checkout
To revise the most recent commit on the topic edit files and add changes normally and then amend the commit:
$ git commit --amend	git help commit Pro Git: Changing the Last Commit
To revise commits further back on the topic, say the 3rd commit back:
$ git rebase -i HEAD~3 (Substitute the correct number of commits back, as low as 1.) Follow Git's interactive instructions. Preserve the Change-Id: line at the bottom of each commit message.	git help rebase Pro Git: Changing Multiple Commits Pro Git: Rebasing
Return to the previous step to share the revised topic.

Test a Topic

When a patch is submitted, it is tested across the three major platforms before being merged and tested on many platforms and configurations on the nightly dashboard.

If tests fail on a submitted topic, see the previous step on how to submit a revised version. After a topic is merged, please check the next day's nightly dashboard to ensure there are not any regressions. If there are any new warnings or errors, submit a follow-up patch as soon as possible.

When a patch is submitted, MacOSX-Clang, Windows-MSVC, and Linux-GCC builds will start. Once they have finished, the build robots will make a comment on the patch with a link to their results visualized in CDash and mark the patch set as Verified +1 or Not Verified -1. The results are submitted by the Kitware Build Robot Gerrit user.

Builds can be spawned by adding the following comments to a patch set in Gerrit.

request build: all	MacOSX, Linux, Windows
request build: osx	MacOSX
request build: linux	Linux
request build: windows	Windows
request build: python	Python Wrapping (Linux, MacOSX, Windows)
request build: power8	POWER8
request build: cpp11	C++11 (Linux, MacOSX, Windows)
request build: cpp14	C++14 (Linux, MacOSX, Windows)
request build: cpp17	C++17 (Linux, MacOSX, Windows)

Merge a Topic

Only authorized developers with Git push access to itk.org may perform this step.

After a feature topic has been reviewed and approved in Gerrit, merge it into the upstream repository.

Checkout the topic if it is not your current branch:
$ git checkout my-topic	git help checkout
Merge the topic, which is originally forked off the master branch, to master branch:
$ git gerrit-merge (If the merge conflicts follow the printed instructions to resolve them.)	alias.gerrit-merge (push to topic stage and stage ITK merge my-topic) Branch-to-Topic Conflict Resolution

For bug fixes that are ready to be included in the next patch release, please email the release manager, Matt McCormick, for assistance.

Here are the recommended steps to merge a topic to both release and master branches, assuming the topic branch is forked off the release branch:

$ git checkout release

$ git merge --no-ff my-topic

$ git push origin release

and do:

$ git checkout master

$ git merge --no-ff release

$ git push origin master

to merge the release branch back to master.

Delete a Topic

After a topic has been merged upstream, delete your local branch for the topic.

Checkout and update the master branch:
$ git checkout master $ git pullall	git help checkout alias.pullall (pull and submodule update)
Delete the local topic branch:
$ git branch -d my-topic	git help branch
The branch -d command works only when the topic branch has been correctly merged. Use -D instead of -d to force the deletion of an unmerged topic branch (warning - you could lose commits).