REPO_POLICIES: pinning covers what we download ourselves; distribution packages are outside it (#156)

prompts/REPO_POLICIES.md

@@ -1,6 +1,6 @@
 ---
 title: Repository Policies
-last_modified: 2026-11-04
+last_modified: 2026-11-06
 ---
 
 This document covers repository structure, tooling, and workflow standards. Code
@@ -21,13 +21,28 @@ style conventions are in separate documents:
   with the authoritative source as policies evolve.
 
 - **External references must be pinned by cryptographic hash.** This is the
-  single most important rule in this document. It covers everything fetched from
-  a remote source, including:
+  single most important rule in this document. It covers what we download and
+  install ourselves in scripts and Dockerfiles:
     - Docker base images
     - Go modules
-    - Python packages
+    - Python packages from PyPI
     - npm packages
     - GitHub Actions
+    - release archives fetched with `curl` or `wget`
+
+    Packages from the distribution's own package manager are outside this rule.
+    They need no version and no hash, because the distribution is trusted. In a
+    `Dockerfile`, it is the pinned base image's distribution. On a host, it is
+    the host's. The host's package manager stands for its distribution, and that
+    includes nix and brew. Updating the package index and upgrading installed
+    packages are fine too. This command, for example, is allowed:
+
+    ```sh
+    apt update && apt upgrade -y && apt install -y build-essential
+    ```
+
+    A package source that a `Dockerfile` adds itself is not the distribution's
+    own, so its packages are pinned like any other download.
 
     A version tag such as `@v4`, `@latest` or `:3.21` is server-mutable, and
     therefore a remote code execution vulnerability. Reference an external
@@ -44,17 +59,6 @@ style conventions are in separate documents:
     Unverified install scripts are arbitrary remote code execution. Double-check
     every external reference in every file before committing.
 
-    There is one exception: a package from the distribution's own package index
-    needs no version and no hash. Pulling that index is also allowed. The
-    distribution is trusted. In a `Dockerfile`, it is the pinned base image's
-    distribution. On a host, it is the host's. The host's package manager stands
-    for its distribution, and that includes nix and brew. These commands are
-    examples:
-    - `apt-get update`
-    - `apt-get install`
-    - `apk update`
-    - `apk add`
-
     These come from the distribution wherever possible:
     - node, meaning the distribution's newest Node package, such as
       `nodejs-current` on Alpine 3.24
@@ -79,9 +83,6 @@ style conventions are in separate documents:
     - the npm registry
     - `go get`
 
-    A package source that a `Dockerfile` adds itself is not the distribution's
-    own, so the exception does not cover it.
-
 - Every repo with software must have a root `Makefile` with these targets:
     - `make bootstrap`
     - `make setup`