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

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

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