RPM Maintenance

Git branches

RPM development takes place in the git master branch, but releases are created from stable branches when a development cycle is coming to an end. The alpha tarball is traditionally cut from master, but prior to the beta release the tree is branched and the beta and later releases are always created from a branch, not master.

The stable branches follow a common naming scheme:

rpm-4.19.x: all 4.19.x versions are cut from this branch
rpm-4.18.x: all 4.18.x versions are cut from this branch
…

When pulling fixes from git master to stable branches, always use -x to get the automatic cherry-pick commit marker. This way it’s easier to see which patches come from master, and which commit exactly. If a cherry-pick conflicts, see if it’s resolvable with a suitable upstream commit and if not, fix it manually and change the “(cherry picked from commit …)” message into “(backported from commit …)” to mark the difference.

Selecting commits

Crafting a stable release is inherently a manual process which starts by selecting suitable commits from the master branch to cherry-pick or backport into the respective stable branch.

While you can do this directly in git, it is recommended that you first create a text file that lists all commits on the master branch since the last release and mark those that you intend to pick. This approach allows you to:

Keep track of which commits you’ve reviewed so far
Ensure that commits are always picked in chronological order
Email the plan to the team to get feedback
Tweak the plan easily, without having to (re)do any conflict resolution
Use a shell script to automate the cherry-picking
Try out different variants of the plan to see which apply cleanly
Track the plan in a git repo

The rest of this section describes a workflow that involves such a text file, one per stable branch, and helper scripts.

Installing the scripts

Download the following utilities, put them into your $PATH and make them executable:

Also download the following file and place it alongside the above utilities:

common.py

Configuring the scripts

Download the default configuration file and apply it to your git checkout as follows:

git config include.path /path/to/gitconfig

You will also need the GitHub CLI utility which is required for commit grouping. On Fedora, get it with:

dnf install gh

Then, run gh auth login to authenticate with GitHub.

Making a plan

First, generate a plan for the stable branch (e.g. rpm-4.19.x):

git checkout <stable>
git cherry-plan make

This will create a file <stable>.plan in the current directory with a chronological list of commits on master since the branching point, in a format similar to that of git rebase -i, and mark with noop those that have been cherry-picked already.

By default, commits will be grouped by their originating GitHub pull requests. This may take a while on the first run since the script needs to fetch the PR data from GitHub. The data is then cached locally in the .git/changeset/ directory and reused on next runs. This feature can be disabled with the -s0 switch.

For complete usage help, run:

git cherry-plan -h

Updating a plan

To later pull new commits from master into the plan, use:

git cherry-plan pull

Editing a plan

The next step is to go through the unmarked commits and mark those that you intend to include in the release with pick. For each commit you review, ask yourself:

Does it change the ABI or API in an incompatible way?

Generally adding entirely new APIs is okay, any other change is not, except of course to fix behavior bugs.
Does it affect package building in an incompatible way?

For example, adding new types of requires within stable releases is not a good idea (but provides are mostly harmless). New spec sanity checks may seem obvious, but unless its a crasher, chances are somebody is actually (ab)using it and will be unhappy if the package no longer builds. New warnings are generally okay, hard errors often are not.

As a rule of thumb: If a package was buildable with rpm-X.Y.Z then it should also be buildable without changes on rpm-X.Y.Z+1, even if it relies on buggy behavior, except for security issues.
Does it affect package installation in an incompatible way?

Rpm is commonly used to install much older and also newer packages built with other versions than the running version, installation compatibility is hugely important always and even more so within stable branches.

As a rule of thumb: If a package was installable with rpm-X.Y.Z then it should also be installable without changes on rpm-X.Y.Z+1, even if it relies on buggy behavior, except for security issues.

If the answer to any of the above is “yes” then it’s almost certainly not appropriate for a stable maintenance release. Mark such a commit with drop.

The general priorities for stable branches are (descending order):

Regression, crash and security fixes
User visible breakage with no workarounds
User visible breakage with major impact
Other major impact stuff (if budget allows)

Choosing a starting point

You may want to skip any commits that were already reviewed in the last release (if any). For a newly created plan, the last noop commit is a good indication of where the review stopped, but it’s a good idea to look a bit further back, in case some otherwise suitable commits were omitted due to budget constraints and such. In particular, regression or security updates (e.g. rpm-4.19.1.1) tend to include very specific cherry-picks, leaving gaps behind that may contain useful material for the next stable release.

Otherwise, when editing an existing plan, simply start at the first unmarked commit. In either case, it can be handy to keep the previous commits in the plan in case some of them turn out to be needed to resolve a conflict.

Once you’ve chosen your starting point, “cut” the plan in half with the following command:

git cherry-plan cut <commit>

This will insert a “scissors” line below <commit> to mark the starting point and automatically mark any unreviewed commits above that line with drop.

If you leave out the <commit> argument, the first unmarked commit will be chosen as the “cutting” point.

Choosing a commit budget

A useful tool to help you pick and, in particular, not pick stuff, is a “commit budget”. For stable releases, 30 is a good ballpark figure, but of course, feel free to tweak it as needed.

Generally speaking, the budget is for code changes only, so any test and documentation additions or updates do not count and should always be picked if possible. In fact, git cherry-plan is already configured to automatically pick such commits when generating a plan, based on GitHub PR labels (see the config file for the list).

The following command will print a summary of the plan (the number of picks etc.) below the scissors line:

git cherry-plan status

VIM config

If you use VIM, you can add this snippet into your ~/.vimrc to cycle through markers on the current line with the CTRL+SPACE key and do a git show of the current commit with the Enter key.

If you install the git-changeset script into your $PATH, you can type gx to open the current commit’s PR in your default browser.

Lastly, you can check if the plan applies cleanly by pressing F8. This will also move the cursor to the line with the conflicting commit (if any).

Checking a plan

While working on a plan, it may be handy to quickly check whether the current selection of commits would apply cleanly to the stable branch. To do that, run:

git cherry-plan check

This will create a temporary clone of the current checkout, apply the plan to it and print a “success” message or the conflicting commit otherwise.

Once you’re satisfied with your picks, send the plan as a plain-text email to the team and ask for feedback. That way, people can reply directly to the individual commits inline.

In most cases, you may only want to include the lines relevant to this review session. You can use the following command that prints the plan to standard output, with everything above the scissors line cut off:

git cherry-plan dump > email.txt

Applying a plan

Once the plan is ready, make a copy of the plan and create a topic branch for the release (e.g. rpm-4.19.1):

cp <stable>.plan <release>.plan
git checkout -b <release>

Then, apply the plan:

git cherry-plan apply

This will go through each pick commit and run git cherry-pick -x on it.

In case a commit doesn’t apply cleanly, the process will stop and a message will be printed. At that point, proceed with conflict resolution as usual and when committing the changes, make sure to replace the line “(cherry picked from commit …)” with “(backported from commit …)”, then run:

git cherry-plan update

This will update the noop markers in the plan copy so that they reflect the actual branch, i.e. any cherry-picks that were applied successfully above. Continue the process by re-running git cherry-plan apply. If another conflict occurs, repeat the same process until the plan is applied completely.

While preparing the plan, it can be handy to try this out on a throwaway branch every now and then, to make sure you’re not missing some pre-requisite commit(s).

Publishing a plan

Now it’s time to publish the final selection in the form of a pull request from your fork’s <release> branch into the <stable> branch.

In case of maintenance releases, leave it up for commenting for at least a week to allow for community feedback
Review needs a different mindset than new code: look for compatibility and stability issues in particular, as per “Selecting commits” above

Make sure the PR is merged before continuing below.

Must-have content

The following items should be completed before proceeding to release cutting:

All GitHub tickets set to the milestone X.Y.Z are completed. You can check that with the following search query: is:issue is:open milestone:X.Y.Z. If there are some left, make sure they’re handled and then go back as many steps as needed.
Translations are up-to-date. If they weren’t recently updated, do that with the below commands, then commit and push to master (use the commit message “Update translation submodule for new translations”) and finally cherry-pick them onto the stable branch.
```
 git submodule update --init
 cd po/
 git pull origin master
```

Cutting a release

RPM 4.19 has moved to CMake as the build system. Prior releases (4.18 and older) use Automake, though, so the following text will list instructions for both build systems for the time being, until 4.18 goes out of support.

In the following text, the X.Y.Z string denotes the version number that you’re preparing, for example 4.19.1.

Make a release commit:
1. CMake:
  1. Bump VERSION in project() in CMakeLists.txt
  2. Bump RPM_SOVERSION and RPM_LIBVERSION in CMakeLists.txt:
    - Consult the associated comment block in CMakeLists.txt for instructions.
    - soname bumps can only occur at the first version of a new branch (i.e. alpha/beta).
  3. Update the output of “pinned” tests: make pinned
2. Automake:
  1. Bump the version in configure.ac
  2. Bump rpm_version_info (i.e. library soname version info) in the rpm.am file. Basic libtool guidelines for maintenance updates to stable versions apply:
    - Consult the libtool manual
    - soname bumps can only occur at the first version of a new branch (i.e. alpha/beta)
  3. Update the sources for the above (Makefiles, .po regeneration and all): make dist
3. Commit the changes from the previous step with something like “Preparing for X.Y.Z” as the message
Generate the final release tarball:
- CMake: make dist
- Automake: make distcheck
Automake only: Check that the previous step does not introduce any new changes (e.g. git diff).
Unpack the tarball next to the previous version and inspect the differences, watching out for unexpected material. If you find any, STOP, figure it out and go back as many steps as required. Note that the docs/ directory may be omitted in most cases since it typically contains a lot of unimportant, automatically generated changes. To inspect the differences, you can use the following command:

diff --color=always -uNr -x docs rpm-X.Y.Z-1 rpm-X.Y.Z | less -R
Tag the release:

git tag -am "RPM X.Y.Z release" rpm-X.Y.Z-release
Push the tag. This is the point of no return for a given release:

git push rpm-X.Y.Z-release
Upload the bz2 tarball:
1. scp it to rpm@ftp-osl.osuosl.org into the appropriate per-branch directory in ~/ftp/releases/
2. Run the ./trigger-rpm script in the home directory to start mirror process
Create the release notes for rpm.org
1. Generate a changelog: git changelog -m > changelog.md (see git changelog -h for more details)
2. Clone the rpm-web repository (if not cloned yet) and enter it
3. Make a copy of the wiki/Releases/skeleton.md file and name it wiki/Releases/X.Y.Z.md
4. Fill in the blanks, use the contents of changelog.md for the “Summary of changes” section
5. Add an entry to the index.md file announcing the release (see the existing entries for inspiration), copy the Highlights section from changelog.md
6. Copy the entry into the timeline.md file
7. Add an entry to the download.md file
8. Commit the whole lot with a commit message such as “Release X.Y.Z”

Make the release official:

Push the above commit to the remote (this will automatically regenerate the pages)

Send out an announcement mail, typically like this:

 To: rpm-announce@lists.rpm.org, rpm-maint@lists.rpm.org, rpm-list@lists.rpm.org
 Subject: RPM X.Y.Z released!

 [some intro followed by the output of "git changelog"]

 For a complete list of changes, visit:

     https://rpm.org/wiki/Releases/X.Y.Z

Open a new GitHub discussion with the content that’s similar to the email and pin it.

Party!