chore: add reviewfixer configs (#244)

## Add reviewfixer to devShell with dedicated nixpkgs pin

Introduces `reviewfixer.yaml` at the repository root to configure reviewfixer to run against the Claude ACP adapter via `npx @agentclientprotocol/claude-agent-acp`. After a successful fixing turn, it automatically posts a `/coder-agents-review` comment to request re-review.

Adds `reviewfixer` to the Nix devShell by building it from a separate `nixpkgs-reviewfixer` input pinned to `nixos-unstable`. This separate pin is necessary because `reviewfixer` requires Go >= 1.26.2, which is not yet available in the main `nixpkgs` pin. The separate input should be removed once the main pin includes Go >= 1.26.2. Note that running `nix flake update` without `--select` will silently collapse both pins to the same revision; use `nix flake update nixpkgs-reviewfixer` to update only that input.

Upstream tests are skipped in the Nix build because they shell out to `git`, which is unavailable in the Nix build sandbox.

Author: ThomasK33

flake.lock

@@ -3,11 +3,21 @@
 
   inputs = {
     nixpkgs.url = "github:NixOS/nixpkgs/nixos-unstable";
+    # Separate nixpkgs pin used only to build reviewfixer. The main pin is
+    # held back to avoid CI/formatter churn, but reviewfixer requires
+    # Go >= 1.26.2. Remove `nixpkgs-reviewfixer` (and `pkgsReviewfixer`
+    # below) once the main pin includes Go >= 1.26.2
+    # (check: `nix eval nixpkgs#go.version`).
+    #
+    # Note: `nix flake update` (no `--select`) bumps both inputs to the
+    # same rev, silently collapsing this version gap. Use
+    # `nix flake update nixpkgs-reviewfixer` to update this input alone.
+    nixpkgs-reviewfixer.url = "github:NixOS/nixpkgs/nixos-unstable";
     flake-utils.url = "github:numtide/flake-utils";
     treefmt-nix.url = "github:numtide/treefmt-nix";
   };
 
-  outputs = { self, nixpkgs, flake-utils, treefmt-nix, ... }:
+  outputs = { self, nixpkgs, nixpkgs-reviewfixer, flake-utils, treefmt-nix, ... }:
     flake-utils.lib.eachDefaultSystem (system:
       let
         pkgs = import nixpkgs {
@@ -18,6 +28,33 @@
           ];
         };
 
+        pkgsReviewfixer = import nixpkgs-reviewfixer { inherit system; };
+
+        reviewfixer = pkgsReviewfixer.buildGoModule rec {
+          pname = "reviewfixer";
+          version = "0.1.0-beta.0";
+
+          src = pkgsReviewfixer.fetchFromGitHub {
+            owner = "ThomasK33";
+            repo = "reviewfixer";
+            rev = "v${version}";
+            hash = "sha256-hrnSm7ttpyUAtkre9micI2n9smKgzX5AmUcj3bJQjbU=";
+          };
+
+          vendorHash = "sha256-yIWbmHFxmOeXBm5TMRsupy33DC6VAUYvZNSz5wa1yxA=";
+
+          # Upstream tests shell out to `git`, which isn't available in the
+          # Nix build sandbox. Skip the test phase here.
+          doCheck = false;
+
+          meta = with pkgsReviewfixer.lib; {
+            description = "Local harness for working through review feedback on Graphite-managed stacked PRs";
+            homepage = "https://github.com/ThomasK33/reviewfixer";
+            license = licenses.mit;
+            mainProgram = "reviewfixer";
+          };
+        };
+
         treefmt = treefmt-nix.lib.evalModule pkgs {
           projectRootFile = "flake.nix";
           programs = {
@@ -56,6 +93,7 @@
           websocat
           jq
           fzf
+          reviewfixer
           # claude-code
         ];
       in

flake.nix

@@ -0,0 +1,40 @@
+# yaml-language-server: $schema=https://raw.githubusercontent.com/ThomasK33/reviewfixer/v0.1.0-beta.0/reviewfixer.schema.json
+# Config for running reviewfixer against the Claude ACP adapter.
+# reviewfixer automatically addresses PR review findings using an AI agent.
+#
+# Prerequisites:
+# - Use the project's Nix devShell (`nix develop` or `direnv allow`) which
+#   already includes `reviewfixer`; this is the primary dev path here, or
+# - `reviewfixer` CLI installed (`go install github.com/ThomasK33/[email protected]`,
+#   or download a binary from https://github.com/ThomasK33/reviewfixer/releases)
+# - `node` and `npm`/`npx` available on PATH (for the ACP adapter below)
+# - `ANTHROPIC_API_KEY` exported in the shell that launches reviewfixer
+#
+# Usage:
+#   reviewfixer validate --config ./reviewfixer.yaml
+#   reviewfixer --config ./reviewfixer.yaml
+#   reviewfixer run --config ./reviewfixer.yaml
+#
+# If you install the adapter globally instead of using `npx`, you can replace:
+#   command: npx
+#   args: ["-y", "@agentclientprotocol/[email protected]"]
+# with:
+#   command: claude-agent-acp
+
+runtime:
+  kind: acp
+  compact_on_resume: true
+  acp:
+    command: npx
+    args:
+      - -y
+      # Pinned to avoid pulling an unverified `latest` at invocation time;
+      # bump deliberately after reviewing release notes.
+      - "@agentclientprotocol/[email protected]"
+
+review:
+  request:
+    # `/coder-agents-review` is consumed by the external coder-agents-review
+    # bot (not by any workflow in this repository).
+    - mode: comment
+      comment: "/coder-agents-review"