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UPDATING.md

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Updating Third Party Projects

When updating a third party project, any changes to the imported project itself (e.g., the zlib/vtkzlib directory for zlib), should go through the update.sh framework. This framework ensures that all patches to the third party projects are tracked externally and available for (preferably) upstream or other projects also embedding the library.

The projects listed in the imported.md file are already using this setup.

Any updates to projects not listed there should first convert over to this framework.

Updating a Project

Once converted, a project should be updated by applying patches to the repository specified in its update.sh script. Once the changes are merged, pulling the changes involves running the update.sh script. This will update the local copy of the project to the version specified in update.sh (usually a for/foo branch, like for/vtk for example, but may be master or any other Git reference) and merge it into the main tree.

This requires a Git 2.5 or higher due the worktree tool being used to simplify the availability of the commits to the main checkout.

Here's an example of updating the twisted project from tag 17.1.0 to 17.5.0, starting with updating the third-party repo

$ cd twisted/
$ git checkout for/vtk
$ git fetch origin
$ git rebase --onto twisted-17.5.0 twisted-17.1.0
$ git push

Now import into VTK

$ cd vtk/ThirdParty/twisted
$ git checkout -b update_twisted
$ ./update.sh

Now you can review the change and make a merge request from the branch as normal.

Porting a Project

When converting a project, if there are any local patches, a project should be created on GitLab to track it. If the upstream project does not use Git, it should be imported into Git (there may be existing conversions available on Github already). The project's description should indicate where the source repository lives.

Once a mirror of the project is created, a branch named for/foo should be created where patches for the foo project will be applied (i.e., for/vtk for VTK's patches to the project). Usually, changes to the build system, the source code for mangling, the addition of .gitattributes files, and other changes belong here. Functional changes should be submitted upstream (but may still be tracked so that they may be used).

The basic steps to import a project twisted based on the tag twisted-17.1.0 looks like this:

$ git clone https://github.com/twisted/twisted.git
$ cd twisted/
$ git remote add kitware [email protected]:third-party/twisted.git
$ git push -u kitware
$ git push -u kitware --tags
$ git checkout twisted-17.1.0
$ git checkout -b for/vtk
$ git push --set-upstream kitware for/vtk

Making the initial import involves filling out the project's update.sh script in its directory. The update-common.sh script describes what is necessary, but in a nutshell, it is basically metadata such as the name of the project and where it goes in the importing project.

The most important bit is the extract_source function which should subset the repository. If all that needs to be done is to extract the files given in the paths variable (described in the update-common.sh script), the git_archive function may be used if the git archive tool generates a suitable subset.

Make sure update.sh is executable before commit. On Unix, run:

  $ chmod u+x update.sh && git add -u update.sh

On Windows, run:

  $ git update-index --chmod=+x update.sh

Also add an entry to imported.md for the project, and CMakeLists.txt and module.cmake as appropriate.

Process

The basic process involves a second branch where the third party project's changes are tracked. This branch has a commit for each time it has been updated and is stripped to only contain the relevant parts (no unit tests, documentation, etc.). This branch is then merged into the main branch as a subdirectory using the subtree merge strategy.

Initial conversions will require a manual push by the maintainers since the conversion involves a root commit which is not allowed under normal circumstances. Please send an email to the mailing list asking for assistance if necessary.