Git Guard

An OpenCode plugin that blocks destructive git commands before they run. It hooks OpenCode's tool.execute.before event and throws on any bash command containing a destructive git variant - the tool call aborts and the agent sees the block message.

How it works: two layers

Layer	Lives in	What it does
1. Plugin guard (this repo)	OpenCode's tool.execute.before hook	Hard-blocks destructive git ops - the tool call aborts, no prompt. Needs no config.
2. Permission rules (optional)	permission.bash ask/allow globs in your opencode.json	Prompts for mutating-but-recoverable ops (commit, push, rebase, …) so non-destructive git work still gets a human in the loop.

The plugin works standalone - layer 2 is optional. Without the pairing block, non-destructive git commands simply run silently. See the Escape hatch for how OPENCODE_GIT_GUARD_DISABLE=1 interacts with both layers.

The guard in action

Install

Requires Node >= 22.6.

Pick one:

1. From npm

Add the package name to plugin in your opencode.json (global ~/.config/opencode/opencode.json or local project ./opencode.json). Restart OpenCode - it installs via Bun at startup (needs network on first run).

{
  "plugin": ["opencode-git-guard"]
}

2. From local file

Save index.ts as git-guard.ts in your plugins directory don't keep the name index.ts - it can collide:

• ~/.config/opencode/plugins/git-guard.ts - global
• .opencode/plugins/git-guard.ts - per project

Restart OpenCode to load. No extra package.json needed - the only import is type-only and erased at runtime.

3. Via agent

Paste this README into an opencode session and ask it to install both layers (plugin + permission pairing). Review the diff - check the allow rows stayed after the ask rows and it landed in the intended (global vs project) config.

What it blocks

Command	Why
git push --force / -f / --force-with-lease	Remote history rewrite (conservative: blocks --force*)
git push origin :branch / --delete	Remote branch deletion
git push --mirror	Force-overwrites all remote refs, deletes remote-only branches/tags
git reset --hard	Discards working tree + index
git checkout . / git restore .	Discards all local changes
git checkout -f / git switch -f / switch --discard-changes	Discards uncommitted changes on switch
git checkout --orphan / -B	History/branch clobbering
git branch -D / -M / -f / --force	Force branch delete/rename/create
git stash drop / clear	Unrecoverable stash loss
git tag -d / -f / --force	Tag deletion / move
git reflog expire	Removes recovery path
git gc --prune / git prune	Unreachable object loss
git update-ref	Direct ref surgery
git filter-branch / filter-repo	History rewriting
git worktree remove --force / prune	Worktree state loss
git clean -fd / -fdx / --force	Untracked file deletion (clean -n / --dry-run always allowed)

What it deliberately does NOT do

• No allowlisting. Branch-guard plugins exist for that; this one only denies known-destructive variants. Everything else flows to your permission config.
• Not a shell parser. Commands are split on |, ;, &, newlines - same residual risk as any bash hook: eval, heredocs, or unusual substitutions can hide a command. Segments not led by git (sudo git reset --hard, echo $(git push --force)) fail conservative: any destructive match blocks.
• Plain-text mentions can false-positive. Writing those commands as text (e.g. echo, heredoc file writes) is also blocked - use the escape hatch for the rare legitimate case.
• Aliases and flag clusters are not traced. git config alias.x 'push --force' then git x (or -c alias.…=…) evades the guard; combined flags like -fB can slip past single-flag patterns. Deliberate evasion is out of scope - this guard targets accidents.
• Quoted messages are handled: git commit -m "git push --force" is recognized as commit and passed through - a denied push pattern only fires when the segment's first git subcommand actually owns it.

Escape hatch

When starting opencode via terminal use the following command to disable the Git Guard:

OPENCODE_GIT_GUARD_DISABLE=1 opencode

Scope: the plugin only. The env var stops the Git Guard from throwing; it does not touch your permission config. With the recommended pairing installed, destructive ops then fall through to the ask rows and prompt for approval instead of being hard-blocked - exactly what you want for a one-off legitimate git filter-repo. If you add your own deny globs, note they survive the hatch: remove the matching row for the one-off.

Read once at startup. Use it when you legitimately need git filter-repo or similar - not as a default.

Recommended permission pairing

The guard denies outright; layer permission rules so non-destructive git work still gets a human in the loop. Merge this into your existing opencode.json (global ~/.config/opencode/opencode.json or project ./opencode.json) - don't replace the whole file or you'll lose the plugin line from Install:

{
  "permission": {
    "bash": {
      "git status*": "allow",
      "git diff*": "allow",
      "git log*": "allow",
      "git show*": "allow",
      "git commit*": "ask",
      "git push*": "ask",
      "git checkout*": "ask",
      "git switch*": "ask",
      "git restore*": "ask",
      "git reset*": "ask",
      "git rebase*": "ask",
      "git revert*": "ask",
      "git cherry-pick*": "ask",
      "git branch*": "ask",
      "git tag*": "ask",
      "git stash*": "ask",
      "git rm*": "ask",
      "git mv*": "ask",
      "git am*": "ask",
      "git apply*": "ask",
      "git remote*": "ask",
      "git worktree*": "ask",
      "git submodule*": "ask",
      "git notes*": "ask",
      "git reflog*": "ask",
      "git gc*": "ask",
      "git prune*": "ask",
      "git filter-branch*": "ask",
      "git filter-repo*": "ask",
      "git update-ref*": "ask",
      "git clean*": "ask",
      "git clean*--dry-run*": "allow",
      "git clean* -n*": "allow",
      "git stash list*": "allow",
      "git branch --list*": "allow",
      "git tag --list*": "allow"
    }
  }
}

Order matters: OpenCode resolves overlapping rules by last-match-wins, so exemption allow rows must come after the broad ask rows they carve out. This block is pre-ordered correctly.

No deny rows on purpose. The plugin hard-blocks destructive ops with better chain attribution, and unanchored deny globs would keep those commands blocked even with the escape hatch set - defeating its purpose. With this pairing, OPENCODE_GIT_GUARD_DISABLE=1 turns hard blocks into approval prompts: the ask rows above catch every destructive op, so nothing runs silently while the hatch is active. If you want belt-and-suspenders deny globs of your own, add them - but see the Escape hatch caveat.

Testing

npm test   # node >= 22.6 (uses --experimental-strip-types)

70 table-driven cases cover the tricky parsing paths (chain segments, -C dir globals, quoted commit messages, clean -n exemption, subcommand attribution).

License

MIT - see LICENSE.