working-with-jj

Imported from ypares/agent-skills (working-with-jj/SKILL.md). Install upstream with npx skills add ypares/agent-skills --skill working-with-jj. Copyright stays with the author.

JJ (Jujutsu) Version Control Helper

Core Principles

• Change IDs (immutable) vs Commit IDs (content-based hashes that change on edit)
• Operations log - every operation can be undone (progressive: multiple jj undo goes further back, jj redo reverses)
• No staging area - working copy auto-snapshots
• Conflicts don't block - resolve later
• Commits are lightweight - edit freely
• Colocated by default - Git repos have both .jj and .git (since v0.34)
• Three DSLs:
  • revsets: select across revisions - a revision (change) ID is a trivial but fully valid singleton revset
  • filesets: select across files in the repository - a regular filepath is a trivial but fully valid singleton fileset
  • templates: select which info to log and how to show it
  • Many jj commands expect expressions using either of these DSLs, to select what to show/operate on

Essential Commands

jj log -r <revset> [-p]               # View history (--patch/-p: include diffs, --count: just count)
jj log -r <revset> -G                 # -G is short for --no-graph
jj show -r <rev>                      # Show revision details (description + diff)
jj evolog -r <rev> [-p]               # View a revision's evolution
jj new [-A] <base>                    # Create revision and edit it (-A: insert between <base> and its children rather than just on top of base)
jj new --no-edit <base>               # Create without switching
jj edit <rev>                         # Switch to editing revision
jj desc -r <rev> -m "text"            # Set description
jj metaedit -r <rev> -m "text"        # Modify metadata (author, timestamps, description)

jj diff                               # Changes in @
jj diff -r <revset>                   # Changes in revset (need to be contiguous)
jj diff -f <rev1> -t <rev2>           # Differences between two states
jj file show -r <rev> <fileset>       # Show file contents at revision (without switching)
jj file show -r <rev> **/*.md -T '"=== " ++ path ++ " ===\n"'  # Multiple files with path headers
jj restore <fileset>                    # Discard changes to files
jj restore --from <commit-id> <fileset> # Restore from another revision/commit

jj split -r <rev> <paths> -m "text"   # Split into two revisions
jj absorb                             # Auto-squash changes into ancestor commits

jj rebase -s <src> -o <dest>          # Rebase with descendants onto <dest>
jj rebase -r <rev> -o <dest>          # Rebase single revision onto <dest>
# NOTE: -d/--destination is deprecated, use -o/--onto instead

jj file annotate <path>               # Blame: who changed each line
jj bisect run -- <cmd>                # Binary search for bug-introducing commit

Additional Commands

jj undo                               # Undo last operation (progressive - repeat to go further back)
jj redo                               # Redo undone operation
jj sign -r <rev>                      # Cryptographically sign commit
jj unsign -r <rev>                    # Remove signature
jj revert -r <rev>                    # Create commit that reverts changes (replaces old jj backout)
jj tag set <name> -r <rev>            # Create/update local tag
jj tag delete <name>                  # Delete local tag
jj git colocation enable              # Convert to colocated repo
jj git colocation disable             # Convert to non-colocated

Quick Revset Reference

@, @-, @--                            # Working copy, parent(s), grandparent(s)
::@                                   # Ancestors
@::                                   # Descendants
mine()                                # Your changes
conflicted()                          # Has conflicts (renamed from conflict() in v0.33)
visible()                             # Visible revisions (built-in alias)
hidden()                              # Hidden revisions (built-in alias)
description(substring-i:"text")       # Match description (partial, case-insensitive)
subject(substring:"text")             # Match first line only
signed()                              # Cryptographically signed commits
A | B, A & B, A ~ B                   # Union, intersection, difference
change_id(prefix)                     # Explicit change ID prefix lookup
parents(x, 2)                         # Parents with depth
exactly(x, 3)                         # Assert exactly N revisions

See references/revsets.md for comprehensive revset patterns.

Common Pitfalls

1. Use -r not --revisions

jj log -r xyz          # ✅
jj log --revisions xyz # ❌

2. Use --no-edit for parallel branches

jj new parent -m "A"; jj new -m "B"                             # ❌ B is child of A!
jj new --no-edit parent -m "A"; jj new --no-edit parent -m "B"  # ✅ Both children of parent

3. Quote revsets in shell

jj log -r 'description(substring:"[todo]")'    # ✅

4. Use -o/--onto instead of -d/--destination (v0.36+)

jj rebase -s xyz -o main   # ✅ New syntax
jj rebase -s xyz -d main   # ⚠️ Deprecated (still works but warns)

5. Symbol expressions are stricter (v0.32+)

Revset symbols no longer resolve to multiple revisions:

jj log -r abc              # ❌ Error if 'abc' matches multiple change IDs
jj log -r 'change_id(abc)' # ✅ Explicitly query by prefix
jj log -r 'bookmarks(abc)' # ✅ For bookmark name patterns

6. Glob patterns are default in filesets (v0.36+)

jj diff 'src/*.rs'         # Matches glob pattern by default
jj diff 'cwd:"src/*.rs"'   # Use cwd: prefix for literal path with special chars

Scripts

Helper scripts in scripts/. Add to PATH or invoke directly.

Recovery

jj op log              # Find operation before problem
jj op restore <op-id>  # Restore the WHOLE repository (history included) to that state

References

• The jj exe is self-documenting:
  • Run jj help -k bookmarks - JJ bookmarks, how they relate to Git branches and how to push/fetch them from Git remotes
  • Run jj help -k revsets - Revset DSL syntax and patterns
  • Run jj help -k filesets - Filepath selection DSL, ie. how to tell jj commands to operate only on specific files
  • Run jj help -k templates - Template language and custom output
  • All jj subcommands have a pretty detailed --help page
• references/command-syntax.md - Command flag details
• references/batch-operations.md - Complex batch transformations on revision descriptions