A Claude Code plugin that blocks unsafe git subtree commands before Bash runs them.

When a command is blocked, the hook stops it and prints the reason:

guard-git-subtree: blocked git subtree invocation

git subtree pull with a URL is BLOCKED.
git subtree does `git fetch <url>` then `git rev-parse FETCH_HEAD` to get the commit.
...

/plugin install git-subtrees

from the systemfsoftware marketplace, or point Claude Code at a local checkout:

/plugin install /path/to/agent-plugins/git-subtrees

Prerequisites: Deno 2.x on PATH. The plugin resolves its one dependency (just-bash) from Deno's registry cache on first hook run — no build step, no bundled dependencies.

git subtree add|pull|push commands that:

• use a URL instead of a pre-fetched ref — subtree reads FETCH_HEAD, a transient file, so a stale read silently squashes the wrong content,
• omit --prefix — the merge lands at the repository root and can delete files across the repo,
• omit -S/--gpg-sign — subtree commits bypass commit.gpgsign config and land unsigned,
• omit --squash — the entire upstream history is pulled into the object store,
• are push — subtrees are read-only; updates flow downstream only.

Update a vendored subtree by pre-fetching to a named ref, verifying the content, then pulling:

git fetch <url> <branch>:refs/remotes/vendor/<name>
git ls-tree refs/remotes/vendor/<name> -- package.json
git subtree pull --prefix=repos/<name> refs/remotes/vendor/<name> --squash -S -m "update"

The hook exits 0 to allow and 2 to block, with the reason on stderr. Non-Bash tools and malformed payloads always pass (0).

Q: The hook says "deno not found on PATH". A: Install Deno 2.x and restart Claude Code.

Q: First run fails with a network error. A: just-bash is fetched to Deno's registry cache on the first hook run. Run once with network access so the cache warms up.

Development setup and workflow: AGENTS.md.

Apache-2.0