JJ Templating Language

Source: https://docs.jj-vcs.dev/latest/templates/

Use templates only when plain jj log output is insufficient: machine-readable output, conditional formatting, scripting pipelines.

Invocation

jj log -r @ --template '...'                    # Single commit
jj log -r 'trunk()..@' --template '...'         # Range
jj log --no-pager --template '...' | jq ...     # Pipe to tools

Commit Fields

Field	Description
`commit_id` / `.short()`	Full/short commit id
`change_id` / `.short()`	Change identity
`description` / `subject`	Full message / first line
`author.email` / `author.name`	Author metadata
`timestamp`	Commit timestamp
`bookmarks` / `tags`	Lists
`conflict`	Boolean
`is_empty`	Boolean
`divergent`	Boolean
`parents`	List of parent commits

Functions

Function	Example
`format()`	`format("[", change_id.short(), "] ", subject)`
`if(cond, a, b)`	`if(conflict, "⚠", "")`
`short()`	`commit_id.short()`
`json()`	`author.email.json()`
`contains()`	`subject.contains("WIP")`
`truncate(n)`	`description.truncate(80)`
`indent(n)`	`description.indent(4)`
`join()`	`bookmarks.join(", ")`
`map()` / `filter()`	`bookmarks.map(lower())`
`len()`	`parents.len()`

Chaining: bookmarks.filter(!contains("WIP")).map(lower()).join(" ")

Examples

# Minimal
change_id.short() " " subject

# WIP emphasis
format(if(subject.contains("WIP"),"[WIP] ",""), change_id.short(), " ", subject)

# Conflicts
format(if(conflict,"⚠ ",""), change_id.short(), " ", subject)

# Bookmarks
format(change_id.short()," ",bookmarks.join(",")," ",subject)

# JSON output
format(
  '{"change":"', change_id.short().json(), '",',
  '"author":"', author.email.json(), '",',
  '"conflict":', if(conflict, 'true','false'), '}'
)

Revset + Template

# Divergent heads with conflicts
jj log -r 'heads(all()) & conflicts()' --template 'format(change_id.short()," ",subject)'

# Commits ahead of remote
jj log -r 'myfeature - myfeature@origin' --template 'format("AHEAD ", change_id.short())'

Pitfalls

Issue	Fix
Unescaped quotes in JSON	Use `.json()` on dynamic fields
Slow on huge histories	Narrow revset first
Complex templates	Build incrementally with `format()`

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