Maintaining Bug Fix Releases¶
Astropy releases, as recommended for most Python projects, follows a <major>.<minor>.<micro> version scheme, where the “micro” version is also known as a “bug fix” release. Bug fix releases should not change any user- visible interfaces. They should only fix bugs on the previous major/minor release and may also refactor internal APIs or include omissions from previous releases–that is, features that were documented to exist but were accidentally left out of the previous release.
Bug fix releases are typically managed by maintaining one or more bug fix branches separate from the master branch (the release procedure below discusses creating these branches). Typically, whenever an issue is fixed on the Astropy master branch a decision must be made whether this is a fix that should be included in the Astropy bug fix release. Usually the answer to this question is “yes”, though there are some issues that may not apply to the bug fix branch. For example, it is not necessary to backport a fix to a new feature that did not exist when the bug fix branch was first created. New features are never merged into the bug fix branch–only bug fixes; hence the name.
In rare cases a bug fix may be made directly into the bug fix branch without going into the master branch first. This may occur if a fix is made to a feature that has been removed or rewritten in the development version and no longer has the issue being fixed. However, depending on how critical the bug is it may be worth including in a bug fix release, as some users can be slow to upgrade to new major/micro versions due to API changes.
Issues are assigned to an Astropy release by way of the Milestone feature in the GitHub issue tracker. At any given time there are at least two versions under development: The next major/minor version, and the next bug fix release. For example, at the time of writing there are two release milestones open: v0.2.2 and v0.3.0. In this case, v0.2.2 is the next bug fix release and all issues that should include fixes in that release should be assigned that milestone. Any issues that implement new features would go into the v0.3.0 milestone–this is any work that goes in the master branch that should not be backported. For a more detailed set of guidelines on using milestones, see Using Milestones and Labels.
Backporting fixes from master¶
Most fixes are backported using the git cherry-pick command, which applies the diff from a single commit like a patch. For the sake of example, say the current bug fix branch is ‘v0.2.x’, and that a bug was fixed in master in a commit abcd1234. In order to backport the fix, simply checkout the v0.2.x branch (it’s also good to make sure it’s in sync with the main Astropy repository) and cherry-pick the appropriate commit:
$ git checkout v0.2.x $ git pull upstream v0.2.x $ git cherry-pick abcd1234
Sometimes a cherry-pick does not apply cleanly, since the bug fix branch represents a different line of development. This can be resolved like any other merge conflict: Edit the conflicted files by hand, and then run git commit and accept the default commit message. If the fix being cherry-picked has an associated changelog entry in a separate commit make sure to backport that as well.
What if the issue required more than one commit to fix? There are a few possibilities for this. The easiest is if the fix came in the form of a pull request that was merged into the master branch. Whenever GitHub merges a pull request it generates a merge commit in the master branch. This merge commit represents the full difference of all the commits in the pull request combined. What this means is that it is only necessary to cherry-pick the merge commit (this requires adding the -m 1 option to the cherry-pick command). For example, if 5678abcd is a merge commit:
$ git checkout v0.2.x $ git pull upstream v0.2.x $ git cherry-pick -m 1 5678abcd
In fact, because Astropy emphasizes a pull request-based workflow, this is the most common scenario for backporting bug fixes, and the one requiring the least thought. However, if you’re not dealing with backporting a fix that was not brought in as a pull request, read on.
Merge commits and cherry picks for further explanation of the cherry-pick command and how it works with merge commits.
If not cherry-picking a merge commit there are still other options for dealing with multiple commits. The simplest, though potentially tedious, is to simply run the cherry-pick command once for each commit in the correct order. However, as of Git 1.7.2 it is possible to merge a range of commits like so:
$ git cherry-pick 1234abcd..56789def
This works fine so long as the commits you want to pick are actually congruous with each other. In most cases this will be the case, though some bug fixes will involve followup commits that need to back backported as well. Most bug fixes will have an issues associated with it in the issue tracker, so make sure to reference all commits related to that issue in the commit message. That way it’s harder for commits that need to be backported from getting lost.
Making fixes directly to the bug fix branch¶
As mentioned earlier in this section, in some cases a fix only applies to a bug fix release, and is not applicable in the mainline development. In this case there are two choices:
- An Astropy developer with commit access to the main Astropy repository may check out the bug fix branch and commit and push your fix directly.
- Preferable: You may also make a pull request through GitHub against the bug fix branch rather than against master. Normally when making a pull request from a branch on your fork to the main Astropy repository GitHub compares your branch to Astropy’s master. If you look on the left-hand side of the pull request page, under “base repo: astropy/astropy” there is a drop-down list labeled “base branch: master”. You can click on this drop-down and instead select the bug fix branch (“v0.2.x” for example). Then GitHub will instead compare your fix against that branch, and merge into that branch when the PR is accepted.
Preparing the bug fix branch for release¶
There are two primary steps that need to be taken before creating a bug fix release (the rest of the procedure is the same as any other release as described in the release procedure below).
- Any existing fixes to the issues assigned to the current bug fix release milestone, or labeled with the relevant “backport-x.y.z” label must be merged into the bug fix branch.
- The Astropy changelog must be updated to list all issues–especially user-visible issues–fixed for the current release. The changelog should be updated in the master branch, and then merged into the bug fix branch. Most issues should already have changelog entries for them. But it’s typical to forget this, so if doesn’t exist yet please add one in the process of backporting. See Updating and Maintaining the Changelog for more details.
To aid in this process there is a script called suggest_backports.py at https://gist.github.com/embray/4497178. The script is not perfect and still needs a little work, but it will get most of the work done. For example, if the current bug fix branch is called ‘v0.2.x’ run it like so:
$ suggest_backports.py astropy astropy v0.2.x -f backport.sh
This will search GitHub for all issues assigned to the next bug fix release milestone that’s associated with the given bug fix branch (‘v0.2.2’ for example), find the commits that fix those issues, and will generate a shell script called backport.sh containing all the git cherry-pick commands to backport all those fixes.
The suggest_backports.py script will typically take a couple minutes to run, but once it’s done simply execute the generated script from within your local clone of the Astropy repository:
This will checkout the appropriate bug fix branch (‘v0.2.x’ in this example), do a git pull upstream v0.2.x to make sure it’s up to date, and then start doing cherry-picks into the bug fix branch.
As discussed earlier, cherry-pick may result in merge conflicts. If this occurs, the backport.sh script will exit and the conflict should be resolved manually, followed by running git commit. To resume the backport.sh script after the merge conflict, it is currently necessary to edit the script to either remove or comment out the git cherry-pick commands that already ran successfully.
The author of the script hopes to improve it in the future to add git rebase like functionality, such that running backport.sh --continue or backport.sh --skip will be possible in such cases.
It has also been noted that the suggest_backports.py script is not perfect, and can either miss issues that need to be backported, and in some cases can report false positives.
It’s always a good idea before finalizing a bug fix release to look on GitHub through the list of closed issues in the release milestone and check that each one has a fix in the bug fix branch. Usually a quick way to do this is for each issue to run:
$ git log --oneline <bugfix-branch> | grep #<issue>
Most fixes will mention their related issue in the commit message, so this tends to be pretty reliable. Some issues won’t show up in the commit log, however, as their fix is in a separate pull request. Usually GitHub makes this clear by cross-referencing the issue with its PR. A future version of the suggest_backports.py script will perform this check automatically.
Finally, not all issues assigned to a release milestone need to be fixed before making that release. Usually, in the interest of getting a release with existing fixes out within some schedule, it’s best to triage issues that won’t be fixed soon to a new release milestone. If the upcoming bug fix release is ‘v0.2.2’, then go ahead and create a ‘v0.2.3’ milestone and reassign to it any issues that you don’t expect to be fixed in time for ‘v0.2.2’.
The automated portion of the Astropy release procedure uses zest.releaser to create the tag and update the version. zest.releaser is extendable through hook functions–Astropy already includes a couple hook functions to modify the default behavior, but future releases may be further automated through the implementation of additional hook functions. In order to use the hooks, Astropy itself must be installed alongside zest.releaser. It is recommended to create a virtualenv specifically for this purpose.
This may seem like a lot of steps, but most of them won’t be necessary to repeat for each release. The advantage of using an automated or semi-automated procedure is that ensures a consistent release process each time.
Update the list of contributors in the creditsandlicense.rst file. The easiest way to check this is do:$ git shortlog -s
And just add anyone from that list who isn’t already credited.
Install virtualenv if you don’t already have it. See the linked virtualenv documentation for details. Also, make sure that you have cython installed, as you will need it to generate the .c files needed for the release.
Create and activate a virtualenv:$ virtualenv --system-site-packages --distribute astropy-release $ source astropy-release/bin/activate
Obtain a clean version of the Astropy repository. That is, one where you don’t have any intermediate build files. Either use a fresh git clone or do git clean -dfx.
Be sure you’re the “master” branch or, for a bug fix release, on the appropriate bug fix branch. For example, if releasing version 0.2.2 make sure to:$ git checkout v0.2.x
Now install Astropy into the virtualenv:$ python setup.py install
This is necessary for two reasons. First, the entry points for the releaser scripts need to be available, and these are in the Astropy package. Second, the build process will generate .c files from the Cython .pyx files, and the .c files are necessary for the source distribution.
Install zest.releaser into the virtualenv; use --upgrade --force to ensure that the latest version is installed in the virtualenv (if you’re running a csh variant make sure to run rehash afterwards too):$ pip install zest.releaser --upgrade --force
Ensure that all changes to the code have been committed, then start the release by running:$ fullrelease
You will be asked to enter the version to be released. Press enter to accept the default (which will normally be correct) or enter a specific version string. A diff will then be shown of CHANGES.rst and setup.py showing that a release date has been added to the changelog, and that the version has been updated in setup.py. Enter ‘Y’ when asked to commit these changes.
You will then be shown the command that will be run to tag the release. Enter ‘Y’ to confirm and run the command.
When asked “Check out the tag (for tweaks or pypi/distutils server upload)” enter ‘N’: zest.releaser does not offer enough control yet over how the register and upload are performed so we will do this manually until the release scripts have been improved.
You will be asked to enter a new development version. Normally the next logical version will be selected–press enter to accept the default, or enter a specific version string. Do not add ”.dev” to the version, as this will be appended automatically (ignore the message that says ”.dev0 will be appended”–it will actually be ”.dev” without the 0). For example, if the just-released version was “0.1” the default next version will be “0.2”. If we want the next version to be, say “1.0” then that must be entered manually.
You will be shown a diff of CHANGES.rst showing that a new section has been added for the new development version, and showing that the version has been updated in setup.py. Enter ‘Y’ to commit these changes.
When asked to push the changes to a remote repository, enter ‘Y’. This should complete the portion of the process that’s automated at this point.
Check out the tag of the released version. For example:$ git checkout v0.1
Create the source distribution by doing:$ python setup.py sdist
Copy the produced .tar.gz somewhere and verify that you can unpack it, build it, and get all the tests to pass. It would be best to create a new virtualenv in which to do this.
Register the release on PyPI with:$ python setup.py register
Upload the source distribution to PyPI; this is preceded by re-running the sdist command, which is necessary for the upload command to know which distribution to upload:$ python setup.py sdist upload
Update the website to reflect the fact there is now a stable release.
Update Readthedocs so that it builds docs for the corresponding github tag, and set the default page to the new release.
If this was a major/minor release (not a bug fix release) create a bug fix branch for this line of release. That is, if the version just released was “v<major>.<minor>.0”, create bug fix branch with the name “v<major>.<minor>.x”. Starting from the commit tagged as the release, just checkout a new branch and push it to the remote server. For example, after releasing version 0.3, do:$ git checkout -b v0.3.x
Then edit setup.py so that the VERSION variable is '0.3.1.dev', and commit that change. Then, do:$ git push upstream v0.3.x
NoteYou may need to replace upstream here with astropy or whatever remote name you use for the main astropy repository.
The purpose of this branch is for creating bug fix releases like “0.3.1” and “0.3.2”, while allowing development of new features to continue in the master branch. Only changesets that fix bugs without making significant API changes should be merged to the bug fix branches.
- Create a bug fix label on GitHub; this should have the same name as the just created bug fix branch prepended with “backport-”. For the previous example this would be “backport-0.3.x” This label should be applied to all issues that should be backported to the bug fix branch. Also create a milestone for the next bug fix release if it hasn’t been made already.
Creating a MacOS X Installer on a DMG¶
The bdist_dmg command can be used to create a .dmg disk image for MacOS X with a .pkg installer. In order to do this, you will need to ensure that you have the following dependencies installed:
To create a .dmg file, run:
python setup.py bdist_dmg
Note that for the actual release version, you should do this with the Python distribution from python.org (not e.g. MacPorts, EPD, etc.). The best way to ensure maximum compatibility is to make sure that Python and Numpy are installed into /Library/Frameworks/Python.framework using the latest stable .dmg installers available for those packages. In addition, the .dmg should be build on a MacOS 10.6 system, to ensure compatibility with 10.6, 10.7, and 10.8.
Before distributing, you should test out an installation of Python, Numpy, and Astropy from scratch using the .dmg installers, preferably on a clean virtual machine.