vcs-detect

name	vcs-detect
description	Detect whether the current project uses jj (Jujutsu) or git for version control. Run this BEFORE any VCS command to use the correct tool.

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

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