jj

<objective> Provide expert guidance for JJ version control operations. Help users understand JJ's mental model (immutable change IDs, auto-snapshots, conflicts don't block) and execute commands correctly. </objective>

<quick_start>

jj log -r <revset> [-p]               # View history (-p: diffs)
jj show -r <rev>                      # Revision details
jj new [-A] <base>                    # Create revision (-A: insert after)
jj edit <rev>                         # Switch to revision
jj desc -r <rev> -m "text"            # Set description
jj diff                               # Changes in @
jj restore <fileset>                  # Discard changes
jj rebase -s <src> -o <dest>          # Rebase onto dest
jj undo                               # Undo last operation

</quick_start>

<success_criteria>

• JJ operation completed without error
• Working copy (@) in expected state
• Revision graph reflects intended structure
• For rebases/splits: no unintended conflicts introduced </success_criteria>

<core_principles>

• Change IDs (immutable) vs Commit IDs (content-hash, changes on edit)
• Operations log: every operation can be undone (progressive jj undo, 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 revisions (a change ID is a valid singleton revset)
  • filesets: select files (a filepath is a valid singleton fileset)
  • templates: control output format </core_principles>

<essential_commands>

jj log -r <revset> [-p]               # View history (--patch/-p: include diffs)
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 after 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 <rev>                      # Changes in revision
jj file show -r <rev> <fileset>       # Show file contents at revision
jj restore <fileset>                  # Discard changes to files
jj restore --from <commit-id> <fileset> # Restore from another revision

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
jj rebase -s 'a | b | c' -o <dest>    # Batch: multiple roots via revset union

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

</essential_commands>

<additional_commands>

jj undo                               # Undo last operation (progressive)
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
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

</additional_commands>

<revset_reference>

@, @-, @--                            # Working copy, parent(s), grandparent(s)
::@                                   # Ancestors
@::                                   # Descendants
mine()                                # Your changes
conflicted()                          # Has conflicts
visible()                             # Visible revisions
hidden()                              # Hidden revisions
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

</revset_reference>

<anti_patterns> <pitfall name="use-short-flag"> Use -r not --revisions:

jj log -r xyz          # correct
jj log --revisions xyz # error

</pitfall> <pitfall name="parallel-branches"> Use `--no-edit` for parallel branches: ```bash 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 ``` </pitfall> <pitfall name="quote-revsets"> Quote revsets in shell: ```bash jj log -r 'description(substring:"[todo]")' ``` </pitfall> <pitfall name="use-onto"> Use `-o`/`--onto` instead of deprecated `-d`/`--destination` (v0.36+): ```bash jj rebase -s xyz -o main # correct jj rebase -s xyz -d main # deprecated ``` </pitfall> <pitfall name="symbol-expressions"> Symbol expressions are stricter (v0.32+). Revset symbols no longer resolve to multiple revisions: ```bash jj log -r abc # error if 'abc' matches multiple change IDs jj log -r 'change_id(abc)' # explicit prefix query jj log -r 'bookmarks(abc)' # for bookmark name patterns ``` </pitfall> <pitfall name="glob-patterns"> Glob patterns are default in filesets (v0.36+): ```bash jj diff 'src/*.rs' # matches glob pattern by default jj diff 'cwd:"src/*.rs"' # use cwd: prefix for literal path ``` </pitfall> <pitfall name="description-glob-brackets"> Don't use glob with `[` brackets in description() - they're character classes: ```bash jj log -r 'description(glob:"*[task:*]*")' # WRONG - [task:*] is char class jj log -r 'description(substring:"[task:")' # CORRECT jj log -r 'tasks()' # BEST - use alias ``` </pitfall>

</anti_patterns>

<recovery>

jj op log              # Find operation before problem
jj op restore <op-id>  # Restore WHOLE repository to that state

</recovery>

<reference_guides>

• Run jj help -k bookmarks - bookmarks, git branches, push/fetch
• Run jj help -k revsets - revset DSL syntax
• Run jj help -k filesets - filepath selection DSL
• Run jj help -k templates - template language
• All subcommands have detailed --help
• references/command-syntax.md - command flag details
• references/batch-operations.md - batch transformations </reference_guides>