If you are a committer, feel free to pick any process that works for you - so long as you are planning to commit the work yourself.

Patch based Contribution

Here is how committing and merging will usually look for merging and pushing for tickets that follow the convention (if patch-based):

Hypothetical CASSANDRA-12345 ticket is a cassandra-4.0 based bug fix that requires different code for cassandra-4.0, cassandra-4.1, and trunk. Contributor Jackie supplied a patch for the root branch (12345-4.0.patch), and patches for the remaining branches (12345-4.1.patch, 12345-5.0.patch, 12345-trunk.patch).

On cassandra-4.0

  1. git am -3 12345-4.0.patch (any problem b/c of CHANGES.txt not merging anymore, fix it in place)

  2. ant realclean && ant jar (rebuild to make sure code compiles)

  3. git commit --amend (Notice this will squash the 4.0 applied patch into the forward merge commit)

On cassandra-4.1

  1. git merge cassandra-4.0 -s ours --log

  2. git apply -3 12345-4.1.patch (any issue with CHANGES.txt : fix and git add CHANGES.txt)

  3. ant realclean && ant jar (rebuild to make sure code compiles)

  4. git commit --amend (Notice this will squash the 4.1 applied patch into the forward merge commit)

On cassandra-5.0

  1. git merge cassandra-4.1 -s ours --log

  2. git apply -3 12345-5.0.patch (any issue with CHANGES.txt : fix and git add CHANGES.txt)

  3. ant realclean && ant jar check (rebuild to make sure code compiles)

  4. git commit --amend (Notice this will squash the 4.1 applied patch into the forward merge commit)

On trunk

  1. git merge cassandra-5.0 -s ours --log

  2. git apply -3 12345-trunk.patch (any issue with CHANGES.txt : fix and git add CHANGES.txt)

  3. ant realclean && ant jar check (rebuild to make sure code compiles)

  4. git commit --amend (Notice this will squash the trunk applied patch into the forward merge commit)

On any branch

  1. git push origin cassandra-4.0 cassandra-4.1 cassandra-5.0 trunk --atomic -n (dryrun check)

  2. git push origin cassandra-4.0 cassandra-4.1 cassandra-5.0 trunk --atomic

Git branch based Contribution

Same scenario, but a branch-based contribution:

On cassandra-4.0

  1. git cherry-pick <sha-of-4.0-commit> (any problem b/c of CHANGES.txt not merging anymore, fix it in place)

  2. ant realclean && ant jar (rebuild to make sure code compiles)

On cassandra-4.1

  1. git merge cassandra-4.0 -s ours --log

  2. git format-patch -1 <sha-of-4.1-commit> (alternative to format-patch and apply is cherry-pick -n)

  3. git apply -3 <sha-of-4.1-commit>.patch (any issue with CHANGES.txt : fix and git add CHANGES.txt)

  4. ant realclean && ant jar (rebuild to make sure code compiles)

  5. git commit --amend (Notice this will squash the 4.1 applied patch into the forward merge commit)

On cassandra-5.0

  1. git merge cassandra-4.1 -s ours --log

  2. git format-patch -1 <sha-of-5.0-commit> (alternative to format-patch and apply is cherry-pick -n)

  3. git apply -3 <sha-of-5.0-commit>.patch (any issue with CHANGES.txt : fix and git add CHANGES.txt)

  4. ant realclean && ant jar check (rebuild to make sure code compiles)

  5. git commit --amend (Notice this will squash the 5.0 applied patch into the forward merge commit)

On trunk

  1. git merge cassandra-5.0 -s ours --log

  2. git format-patch -1 <sha-of-trunk-commit> (alternative to format-patch and apply is cherry-pick -n)

  3. git apply -3 <sha-of-trunk-commit>.patch (any issue with CHANGES.txt : fix and git add CHANGES.txt)

  4. ant realclean && ant jar check (rebuild to make sure code compiles)

  5. git commit --amend (Notice this will squash the trunk applied patch into the forward merge commit)

On any branch

  1. git push origin cassandra-4.0 cassandra-4.1 cassandra-5.0 trunk --atomic -n (dryrun check)

  2. git push origin cassandra-4.0 cassandra-4.1 cassandra-5.0 trunk --atomic

Contributions only for release branches

If the patch is for an older branch, and doesn’t impact later branches (such as trunk), we still need to merge up.

On cassandra-4.0

  1. git cherry-pick <sha-of-4.0-commit> (any problem b/c of CHANGES.txt not merging anymore, fix it in place)

  2. ant realclean && ant jar (rebuild to make sure code compiles)

On cassandra-4.1

  1. git merge cassandra-4.0 -s ours --log

  2. ant realclean && ant jar (rebuild to make sure code compiles)

On cassandra-5.0

  1. git merge cassandra-4.1 -s ours --log

  2. ant realclean && ant jar check (rebuild to make sure code compiles)

On trunk

  1. git merge cassandra-4.1 -s ours --log

  2. ant realclean && ant jar check (rebuild to make sure code compiles)

On any branch

  1. git push origin cassandra-4.0 cassandra-4.1 trunk --atomic -n (dryrun check)

  2. git push origin cassandra-4.0 cassandra-4.1 trunk --atomic

Tips

Tip

A template for commit messages:

  1. <One sentence description, usually Jira title or CHANGES.txt summary>
  2. <Optional lengthier description>
  4. patch by <Authors>; reviewed by <Reviewers> for CASSANDRA-#####
  6. Co-authored-by: Name1 <email1>
  7. Co-authored-by: Name2 <email2>
Tip

Notes on git flags: -3 flag to am and apply will instruct git to perform a 3-way merge for you. If a conflict is detected, you can either resolve it manually or invoke git mergetool - for both am and apply.

—atomic flag to git push does the obvious thing: pushes all or nothing. Without the flag, the command is equivalent to running git push once per each branch. This is nifty in case a race condition happens - you won’t push half the branches, blocking other committers’ progress while you are resolving the issue.

Tip

The fastest way to get a patch from someone’s commit in a branch on GH - if you don’t have their repo in remotes - is to append .patch to the commit url, e.g. curl -O github.com/apache/cassandra/commit/7374e9b5ab08c1f1e612bf72293ea14c959b0c3c.patch

Tip

git cherry-pick -n <sha-of-X.X-commit> can be used in place of the git format-patch -1 <sha-of-X.X-commit> ; git apply -3 <sha-of-X.X-commit>.patch steps.