# Vcs Detect

> Detect whether the current project uses jj (Jujutsu) or git for version control. Run this BEFORE any VCS command to use the correct tool. Use when this capability is needed.

- Skill: `tomevault-io/vcs-detect` (Agent Skill, multi-file: 2 files)
- Install (CLI): `npx skillmds@latest add tomevault-io/vcs-detect`
- Raw SKILL.md: https://api.skillmd.com/api/skills/tomevault-io/vcs-detect/raw
- Safety review: pending (external: skill-scanner PASS, skillspector PASS)
- Works with: Claude Code, Claude.ai, OpenAI Codex
- Category: Coding & Dev Tools
- Author: tomevault-io (https://skillmd.com/u/tomevault-io)
- Updated: 2026-09-17
- Page: https://skillmd.com/skills/tomevault-io/vcs-detect

---


# VCS Detection Skill

Detect the version control system in use before running any VCS commands.

## Why This Matters

- jj (Jujutsu) and git have different CLIs and workflows
- Running `git` commands in a jj repo (or vice versa) causes errors
- Some repos use jj with git colocated (both `.jj/` and `.git/` exist)

## Detection Logic

Both `jj root` and `git rev-parse --show-toplevel` walk up the filesystem to find repo root.

**Priority order:**

1. `jj root` succeeds → jj (handles colocated too)
2. `git rev-parse` succeeds → git
3. Both fail → no VCS

## Detection Command

```bash
if jj root &>/dev/null; then echo "jj"
elif git rev-parse --show-toplevel &>/dev/null; then echo "git"
else echo "none"
fi
```

## Command Mappings

| Operation   | git                      | jj                          |
| ----------- | ------------------------ | --------------------------- |
| Status      | `git status`             | `jj status`                 |
| Log         | `git log`                | `jj log`                    |
| Diff        | `git diff`               | `jj diff`                   |
| Commit      | `git commit`             | `jj commit` / `jj describe` |
| Branch list | `git branch`             | `jj branch list`            |
| New branch  | `git checkout -b <name>` | `jj branch create <name>`   |
| Push        | `git push`               | `jj git push`               |
| Pull/Fetch  | `git pull` / `git fetch` | `jj git fetch`              |
| Rebase      | `git rebase`             | `jj rebase`                 |

## Usage

Before any VCS operation:

1. Run detection command
2. Use appropriate CLI based on result
3. If `none`, warn user directory is not version controlled

## Example Integration

```
User: Show me the git log
Agent: [Runs detection] -> Result: jj
Agent: [Runs `jj log` instead of `git log`]
```

## Colocated Repos

When both `.jj/` and `.git/` exist, the repo is "colocated":

- jj manages the working copy
- git is available for compatibility (GitHub, etc.)
- **Always prefer jj commands** in colocated repos

---
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<!-- tomevault:4.0:skill_md:2026-04-16 -->