Agent skill

jj-hunk

Programmatic hunk selection for jj (Jujutsu). Use when splitting commits, making partial commits, or selectively squashing changes without interactive UI.

View SKILL.md on GitHub Repository
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Install this agent skill to your Project

npx add-skill https://github.com/knoopx/pi/tree/main/agent/skills/jj-hunk

SKILL.md

jj-hunk

Programmatic hunk selection for Jujutsu. Split, commit, or squash specific hunks without interactive prompts.

Quick Start

bash
# List hunks in current changes
jj-hunk list

# List hunks for a specific revision
jj-hunk list --rev @-

# Split hunks 0,1 of foo.rs into first commit, rest into second
jj-hunk split '{"files": {"src/foo.rs": {"hunks": [0, 1]}}, "default": "reset"}' "first commit"

Commands

Command Description
jj-hunk list [options] List hunks, files, or spec templates
jj-hunk split [-r rev] <spec> <message> Split changes into two commits
jj-hunk commit <spec> <message> Commit selected hunks
jj-hunk squash [-r rev] <spec> Squash selected hunks into parent

List Options

Option Description
--rev <revset> Diff revision against parent
--format json|yaml|text Output format (default: json)
--include <glob> / --exclude <glob> Filter paths (repeatable)
--group none|directory|extension Group output
--files List files with hunk counts only
--spec-template Emit a spec template (JSON/YAML only)

Spec Format

Specs are JSON or YAML. Select hunks by index (0-based) or by stable ids.

json
{
  "files": {
    "path/to/file": { "hunks": [0, 1] },
    "path/to/other": { "ids": ["hunk-9a2b..."] },
    "path/to/another": { "action": "keep" },
    "path/to/skip": { "action": "reset" }
  },
  "default": "reset"
}
Action Description
{"hunks": [0, 1]} Select by index (0-based)
{"ids": ["hunk-..."]} Select by stable ID from jj-hunk list
{"action": "keep"} Keep all changes in file
{"action": "reset"} Discard all changes in file
"default" Action for unlisted files

Example: Split by Hunk

Scenario: You have multiple changes in one commit. Split them logically.

bash
# 1. See what hunks exist
jj-hunk list --format text

Output:

M src/main.rs
  hunk 0 insert hunk-abc123 (before 1+0 after 1+10)
  hunk 1 insert hunk-def456 (before 1+0 after 1+5)
M src/lib.rs
  hunk 0 insert hunk-789xyz (before 1+0 after 1+8)
bash
# 2. Split: first hunk of main.rs → commit A, rest → commit B
jj-hunk split '{"files": {"src/main.rs": {"hunks": [0]}}, "default": "reset"}' "feat: add feature A"

# 3. The remaining changes stay in working copy
jj diff --name-only
# src/main.rs (hunk 1), src/lib.rs

Example: Split Multiple Files

bash
# List hunks
jj-hunk list --format yaml
bash
# Create spec file
cat > /tmp/split-spec.yaml << 'EOF'
files:
  pkgs/new-tool.nix:
    action: keep
  modules/home-manager/packages/cli.nix:
    hunks: [0]
  flake.nix:
    hunks: [0]
default: reset
EOF

# Split using spec file
jj-hunk split --spec-file /tmp/split-spec.yaml "feat(cli): add new-tool"

Example: Commit Subset of Changes

bash
# Commit only the fix, leave experimental code uncommitted
jj-hunk commit '{"files": {"src/fix.rs": {"action": "keep"}}, "default": "reset"}' "fix: handle edge case"

Example: Squash Specific Changes

bash
# Squash cleanup into parent commit
jj-hunk squash '{"files": {"src/cleanup.rs": {"action": "keep"}}, "default": "reset"}'

Example: Split by File Pattern

bash
# Commit all test files, keep source changes
jj-hunk commit '{"files": {}, "default": "reset"}' "test: add tests"
# Then filter with --include
jj-hunk list --include '**/*.test.rs' --format yaml

Tips

  • Use --spec-template to generate an ID-based spec:
    bash
    jj-hunk list --spec-template --format yaml > /tmp/spec.yaml
  • IDs are stable (sha256-based), indices are not
  • Use --files for a quick summary:
    bash
    jj-hunk list --files --format text
  • Read spec from stdin:
    bash
    cat spec.json | jj-hunk commit - "message"

Related Skills

  • jujutsu: General jj commands and workflows
  • conventional-commits: Commit message format

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