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skills/git-jj/references/jj_template.md

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+# 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
+
+```bash
+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
+
+```bash
+# 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
+
+```bash
+# 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()` |