split

Split a branch into multiple stacked branches. This is useful when you’ve accumulated multiple logical changes in a single branch and want to break them into separate, focused PRs for easier review.

Usage

rung split
rung split feature/big-change
rung split --dry-run
rung split --abort

Aliases

• rung sp — shorthand for rung split

Options

Option	Description
--dry-run	Show what would be done without making changes
--abort	Abort the current split and restore from backup

How It Works

When you run rung split:

1. Analyze — Lists all commits between the parent branch and the current branch
2. Select — Interactive UI lets you select commits to split off into new branches
3. Name — Prompts for branch names (suggests names based on commit messages)
4. Create — Creates new branches at each split point
5. Update Stack — Reparents the original branch onto the last created branch

Example

Split a branch with multiple commits into separate stacked branches:

$ rung split
Commits in feat-big-change (oldest first):

  1. a1b2c3d4 Add user model
  2. e5f6g7h8 Add user API endpoints
  3. i9j0k1l2 Add user tests

Select commits to split (space to toggle, enter to confirm):
  [x] a1b2c3d4 Add user model
  [x] e5f6g7h8 Add user API endpoints
  [ ] i9j0k1l2 Add user tests

Branch name for "Add user model" [feat-add-user-model]:
Branch name for "Add user API endpoints" [feat-add-user-api]:

✓ Created branch feat-add-user-model at a1b2c3d4
✓ Created branch feat-add-user-api at e5f6g7h8
✓ Reparented feat-big-change onto feat-add-user-api

Stack after split:
  main
  └── feat-add-user-model
      └── feat-add-user-api
          └── feat-big-change

Dry Run

Preview the split without making changes:

$ rung split --dry-run
Commits in feat-big-change (oldest first):

  1. a1b2c3d4 Add user model
  2. e5f6g7h8 Add user API endpoints

Would create:
  main
  └── feat-add-user-model (at a1b2c3d4)
      └── feat-add-user-api (at e5f6g7h8)
          └── feat-big-change

Dry run - no changes made

Aborting a Split

If something goes wrong during the split, you can restore your branches to their pre-split state:

rung split --abort

This restores the original branch and removes any partially created branches.

Split State

During a split operation, rung writes state to .git/rung/split_state.json:

{
  "started_at": "2024-01-15T10:30:00Z",
  "backup_id": "1704067200",
  "source_branch": "feat-big-change",
  "parent_branch": "main",
  "original_branch": "feat-big-change",
  "split_points": [
    {
      "commit_sha": "a1b2c3d4...",
      "branch_name": "feat-add-user-model"
    }
  ],
  "current_index": 0,
  "completed": [],
  "stack_updated": false
}

This allows --abort to restore the original state if needed.

Branch Naming

Rung suggests branch names based on commit messages:

• Extracts the first few words from the commit summary
• Converts to kebab-case (lowercase with hyphens)
• Falls back to <source-branch>-part-N if the message can’t be parsed

You can accept the suggestion or type a custom name for each branch.

Workflow Example

# You've been working on a feature and it grew too large
$ rung log
a1b2c3d    Add user model                  you
e5f6g7h    Add user API endpoints          you
i9j0k1l    Add user authentication         you
m2n3o4p    Add user tests                  you

# Split into focused branches for review
$ rung split
# Select commits, provide names

# After splitting:
$ rung status
main
└── feat-add-user-model (#101)
    └── feat-add-user-api (#102)
        └── feat-add-user-auth (#103)
            └── feat-add-user-tests

# Submit PRs for the new branches
$ rung submit

Notes

• The split operation creates a linear chain of branches from the selected commits
• Each split point becomes a new branch that is a parent of the next
• The original branch is reparented onto the last created branch
• Always commit or stash your changes before splitting
• Use --dry-run to preview the resulting stack structure
• Backup refs are stored in .git/rung/backups/ for undo capability

Limitations

• Cannot split a root branch (must have a parent in the stack)
• The branch being split must have at least one commit above its parent
• Split points must be selected in order (oldest to newest)

Related Commands

• create — Create a new branch in the stack
• restack — Move a branch to a different parent
• log — See commits in the current branch
• undo — Restore from last backup