Stacker

Easy git rebasing of stacked feature branches

Audience

Stacker is recommended for a workflow where * individual contributors work in the same repository, * commits are made to dev branches that are forked from the main or a topic branch, * each dev branch is completely owned and used by the one contributor and * contributors are expected to provide a clean commit history (without merges) for review.

Stacker helps with managing entire stacks of these dev branches, i.e. when they are branched off of and depend on each other, allowing for a more rapid development. While one branch is undergoing review another branch can be stacked onto it and worked in.

Workflow

1. Create a new branch.

   stacker start my-new-feature

2. Do some work.

   git add .... git commit .... Repeat.

3. Meanwhile the base branch has merges from other contributors. Fetch everything.

   stacker sync

4. Rebase the branch, so it forks off at the head of the base branch.

   stacker rebase

5. Publish the branch by pushing it the first time.

   stacker push

6. Oh, there's a bad commit.

   git rebase -i HEAD~5

7. Now the local branch and the remote branch divert. Push again to (forcefully) set remote branch to what local branch points at.

   stacker push

Usage

``` stacker 0.1.0

Easy stacking of dev branches in git repositories.

USAGE: stacker

OPTIONS: -h, --help Print help information -V, --version Print version information

SUBCOMMANDS: clean Cleans any stacker related refs and settings from repo. fix Adds, updates and deletes tracking refs if needed. help Print this message or the help of the given subcommand(s) init Initializes the repo and tries to set stacker refs for any non-default branches. push Sets remote branch head to what local branch head points to. rebase Rebases current branch on top of its base branch. start Starts a new branch off of current branch. sync Fetches all branches and tags and prunes deleted ones. ```

Under the Hood

Tracking Refs

Stacker uses custom refs to track branches:

• refs/stacker/base/<branchname>

  A symref to the parent branch in the stack. Created when a branch is created. Only updated when a branch is moved within the stack. Deleted when either branch is deleted.

• refs/stacker/start/<branchname>

  The commit where the branch starts. Created when a branch is created. Updated after a rebase. Deleted when the branch is deleted.

• refs/stacker/remote/<branchname>

  The commit where the remote branch head is expected to be. Created when a branch is pushed for the first time. Updated after a push. Deleted when the branch is deleted.

Stacker does not update/delete any refs outside refs/stacker/.

Config

Stacker puts a few settings into $REPO/.git/config:

• log.excludeDecoration = refs/stacker/

  To hide the trackings refs in git log output.

• transfer.hideRefs = refs/stacker/

  Probably over-paranoid. Just so there's no possibility these refs leave the local repo.

• stacker.*

  Any stacker specific settings.

Stacker will only touch the repo's config. It's safe to make these settings in --global or --system.

Git Commands

Stacker mainly uses two commands to manage branches:

• git rebase --committer-date-is-author-date --onto refs/stacker/base/<branch> refs/stacker/start/<branch> <branch>

  Rebases a branch onto its base branch starting at start marker. If there are conflict, rebasing will stop. Fix conflicts and use --continue or --abort. After a successful rebase the start marker ref will be moved.

• git push --set-upstream --force-with-lease=<branch>:<expected-commit> <remote> <branch>:<branch>

  Pushes a branch to remote, potentially replacing the commit chain, so the remote branch looks exactly like the local branch. <expected-commit> is what refs/stacker/remote/<branch> points to.

In addition, Stacker uses a few more commands to help keeping track of things, like for-each-ref, update-ref, symbolic-ref, check-ref-format.