Branches

The OpenCV repository has several branches with different contribution policies.

Common rules for all branches

Your development branch name must differ from the names of branches in the upstream OpenCV repository, i.e. your branch must NOT be named 2.4, 3.4, 4.x, 5.x, or master/next (it's a technical requirement specific to our continuous integration system to properly test multi-repository patches with opencv_extra/opencv_contrib)
Multiple related commits should be squashed into one. A pull request must contain either a single commit, or several unrelated commits (e.g, commit with test + commit with code fix)

Branches and contribution policies in OpenCV

Please target Pull Requests (PR) to the right branches. Quick summary of the rules is presented in the table below. More formal description is in the sections after the table.

Which branch should I target my PR?

Policy	5.x	4.x
Preserve API compatibility	✔️	✔️
Preserve ABI compatibility	❌	❌❕
Change applicable only to this branch	✔️	✔️
Bugfix / minor fix	👉	✔️
Optimization	👉	✔️
Small feature	👉	✔️
Large feature	✔️	❌
Branch alias (do not use!)	next	master

❕ - avoid major breakages
👉 - rebase to previous branch if patch is applicable, it will be ported to other branches by the Core team in a week or two

5.x

This is the development branch for upcoming 5.x releases.

API compatibility must be preserved
If your pull request contains a bug fix which is also applicable to the 3.4 or 4.x branch, you should choose that branch as "base"
If you've already created pull request based on the 5.x branch, but it is also applicable to 4.x, you will be asked to rebase it to 4.x/3.4 branches, see the instruction in the following section.

4.x

This is the branch for 4.x releases.

API compatibility must be preserved
Incompatible improvements or large features should be targeted to 5.x branch
Compatible improvements or small features should go to 4.x branch
If your pull request contains a bug fix which is also applicable to the 3.4 branch, you should choose that branch as "base"
If you've already created pull request based on the 4.x branch, but it is also applicable to 3.4, you will be asked to rebase it to 3.4, see the instruction in the following section.
We will merge changes from 4.x into 5.x regularly (weekly/bi-weekly) There is no regular process for backporting patches from 5.x branch

EOL branches

EOL branches:

"3.4": this is the branch for 3.4.x releases. This release series is EOL in 2023. CI is turned off, so no more patches are accepted to 3.4 branch.
"2.4": this is the branch for 2.4.x releases. This release series is EOL in 2020. CI is turned off, so no more patches are accepted to 2.4 branch.

master / next

"master" branch is a shadow copy of 4.x development branch kept for compatibility purposes. After 5.0 release this branch will shadow 5.x branch. "next" branch is a shadow copy of 5.x development branch kept for compatibility purposes. It will be removed after 5.0 release. Merge to this branches is prohibited. Use 4.x / 5.x as target branches for your PRs.

Rebasing a pull request between branches

If you can not do this by yourself, please ask maintainers for help.

Example of rebasing from 5.x branch to 4.x branch:

do not close the existing pull request
change the "base" branch of the pull request:
- open PR on GitHub in your browser
- press the "Edit" button near the pull request title
- choose "4.x" from the dropdown list
rebase your commits from 5.x onto 4.x:
- git checkout <your-branch>
- (optional) create a backup branch: git branch <your-branch>-backup
- git remote update upstream (assuming upstream is pointing to the opencv/opencv GitHub repository)
- git rebase -i --onto upstream/4.x upstream/5.x
- an editor will be opened. Please check the list of commits - there should be only your commits - save and exit
- git push --force origin <your-branch> (assuming origin is pointing to <your-username>/opencv forked GitHub repository)

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