Squid Merge Procedure

The requirements outlined in this document are meant to speedup acceptance of code changes while reducing rewrites, minimizing conflicts, and maintaining high quality of the committed code. If the requirements need changing, please discuss before violating them. Other than that, please use common sense and do what you think is in the best interest of Squid.

  1. #Before_you_start_coding, make sure your future changes are welcomed and coordinate your plans with other developers.

  2. Implement your changes while following SquidCodingGuidelines. Use git for version control (see GitHints).

  3. Complete #Submission_Checklist.

  4. Submit a #Pull_Request on GitHub.

  5. Monitor for automated test failures and work with reviewers to get enough #Votes, updating your pull request as needed.

  6. Remind Core Developers to merge your eligible pull request as needed (until merging is automated).

  7. Enjoy your code becoming official!
  8. Support your changes by addressing bug reports and answering related development questions.

Before you start coding

Before spending time coding, please discuss your plans on the squid-dev mailing list so that others can

  • confirm that the proposed feature is not already supported and is welcomed,
  • assist you in finding the best way to add your feature, and
  • prevent duplication of effort (somebody else might be working on similar changes already).

Submission Checklist

If you are sure that an item does not apply to your specific situation, just skip it (at your own risk).

  1. The code is ready to be published and distributed under the Squid licensing terms.
  2. Release notes updated: doc/release-notes/release-X.sgml. Don't worry about the HTML or TXT files, they are automatically built by the maintainer. Only the SGML files need updating.

  3. The feature sponsor is added to the SPONSORS.list file.
  4. Copyright statement and license for newly imported code are added to the CREDITS file.
  5. Development branch rebased on top of the official master branch.
  6. git diff --check upstream/master produces no warnings/errors and exits with zero status code. Adjust remote (i.e., "upstream") to match the official repository (i.e., github.com:squid-cache/squid.git) as needed.

  7. ./test-builds.sh succeeds. In the unlikely event the test fails because of the bugs in the official code, file a bug report or discuss on squid-dev. Your future pull request will get stuck if it cannot pass these basic build tests!

Pull Request

All commits to the official repository require a GitHub pull request (PR). This requirement ensures that all official changes are peer reviewed, and all official branches are always in working order (to the extent our testing can detect bugs, of course). It also helps reduce commit noise and backporting overheads. This section documents PR requirements. See GitHints for PR submission recipes.

  1. Please complete #Submission_Checklist before making a pull request. If you really need to post a PR earlier, then start your PR title with a "[WIP] " prefix (six characters indicating a "work in progress") and explain why you are posting an unchecked PR in the PR comment. By default, WIP PRs are not reviewed, but they do go through CI tests.

  2. Please use English and plain text formatting.
  3. PR title is the first line of the anticipated commit message. Be specific but succinct. Do not exceed 65 characters.

  4. PR description is the anticipated commit message body (following the first line described above and a blank line). Avoid detailing your changes (your changes should speak for themselves!). Focus on why you changed the code and on the anticipated impact of your changes. Do not exceed 72 characters per line.

  5. By default, individual PR branch commits will be automatically squash-merged. Thus, you may leave intermediate commits in your branch when posting your PR -- a reviewer should ignore them and review their cumulative result instead. Avoid squashing during GitHub review iterations.

  6. During GitHub review iterations, avoid merging fresh master (or target branch) changes into your PR branch unless such an update becomes necessary. After the PR is approved, your PR branch will be automatically merged into then-current target branch.

  7. A PR commit not authored by you should have the right author set (via git commit --author=... or equivalent).

If you cannot submit your changes in the form of a pull request, find a developer who can do that for you.

Votes

The first matching rule wins. A submission is automatically counted as one positive vote from the submitter.

  • {i} Any developer may vote.

    {i} These rules are not yet fully enforced on GitHub but they (or their next revision) will be. For now, GitHub will not allow to merge your pull request without a core developer (other than you) approval, but all the voting rules still apply.

  • One negative vote by a core developer blocks the merge until resolved.
  • Two positive votes from core developers accept the submission (with a high priority for merging).
  • Any three positive votes accept the submission.
  • Submissions older than 10 days without negative votes are accepted.

Exceptions

In truly exceptional situations (that ought to be disclosed and discussed as soon as possible):

  1. Core developers may commit any changes immediately.
  2. Within 10 days of the commit, core developers may remove any submission without prior notice or discussion. A post-factum notice (and discussion) are still expected on squid-dev.

Core Developers

The core developers mentioned above are experienced developers with serious long-term dedication and contribution to the Squid Project as a whole and Squid code in particular. They are usually active on squid-dev and often review submissions. Core folks have collective responsibility for the Squid Project and may use their super powers to resolve conflicts or prevent disasters.

Automation

The "trusted master" principle enforced by merge automation states that the master branch automatically gets all trusted code changes and nothing else. In this context, an trusted code change is, by definition, a non-empty sequence of git commits that satisfies the following requirements:

  1. the sequence is (the beginning of) an approved pull request branch on GitHub,

  2. the sequence can be merged into master without conflicts, and
  3. the last commit in the sequence has passed all the required QA tests.

Currently, PR branches are squashed when merging. Squashing significantly reduces master noise and ensures that each master commit is trusted because automated tests interrogate the to-be-committed (and usually the latest) PR branch revision. If needed, we can find a way to mark the trusted commits specially while merging unsquashed branches under exceptional circumstances.

Currently, the approval of earlier PR branch revisions automatically extends to all future branch revisions (until manually withdrawn) but that may change or even become configurable on a per-PR basis.

Automated master commits are performed by a program called merge bot. Only the merge bot has the rights to modify master. The Squid Project is currently using the Anubis merge bot with the following configuration:

Field

Description

Value

github_login

The bot uses this GitHub user account for all GitHub communications, including target branch updates. This user needs to have write access to the repository.

"squid-anubis"

staging_branch

The name of the bot-maintained git branch used for testing PR changes as if they were merged into their target branch.

auto

necessary_approvals

The minimal number of core developers required for a PR to be merged. PRs with fewer votes are not merged, regardless of their age.

1

sufficient_approvals

The minimal number of core developers required for a PR to be merged fast (i.e., without waiting for config::voting_delay_max)

2

voting_delay_min

The minimum merging age of a PR. Younger PRs are not merged, regardless of the number of votes. The PR age string should comply with timestring parser.

"2d"

voting_delay_max

The maximum merging age of a PR that has fewer than config::sufficient_approvals votes. The PR age string should comply with timestring parser.

"10d"

staging_checks

The expected number of CI tests executed against the staging branch.

2

guarded_run

Only PRs (manually) labeled M-cleared-for-merge are merged by Anubis.

true

MergeProcedure (last edited 2018-10-25 23:35:34 by AlexRousskov)