Say why the install failed

CHANGELOG.md

@@ -6,6 +6,22 @@ adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0.html).
 
 ## [Unreleased]
 
+### Fixed
+
+- `install.sh` reported a refused request as a repository with no releases. The
+  fetch was piped straight into `sed`, so its exit status was hidden behind
+  `head` and an empty parse looked like an empty repository -- the message sent
+  whoever read it looking in the wrong place. It now reads the response before
+  parsing it, and says what is usually true: GitHub allows 60 unauthenticated
+  API requests an hour per address, CI runners share addresses, and the fix is
+  a token or a pinned version.
+- Downloads retry. A reset connection on the way to a release is not a reason
+  to fail a build.
+- A failed installation says so. In a checks list an install that could not
+  happen and a scan that found something are both a red job ending in `exit
+  code 1`; the action now annotates the first as an installation failure, and
+  points at the `token` input when rate limiting is the cause.
+
 ### Added
 
 - `site/` — the source for [straitjacket.dev](https://straitjacket.dev), moved

action.yml

@@ -75,8 +75,11 @@ inputs:
     default: "true"
   token:
     description: >-
-      Token used to download the release. Needed only while the Straitjacket
-      repository is private; a public release needs none.
+      Token used to read the release. Worth setting even for a public release:
+      GitHub allows 60 unauthenticated API requests an hour per address and CI
+      runners share addresses, so without one this eventually fails to install
+      at all. `${{ github.token }}` is enough; it needs no access to the
+      Straitjacket repository while that repository is public.
     required: false
     default: ""
 
@@ -89,6 +92,7 @@ runs:
   using: composite
   steps:
     - name: Install straitjacket
+      id: install
       shell: bash
       env:
         VERSION: ${{ inputs.version }}
@@ -100,7 +104,13 @@ runs:
         if [ "$VERSION" != "latest" ]; then
           export STRAITJACKET_VERSION="$VERSION"
         fi
-        sh "${ACTION_PATH}/install.sh"
+        # Failing to install is not the same as finding something, and at a
+        # glance in the checks list the two look identical: both are a red job
+        # whose log ends in `exit code 1`. Say which one this is.
+        if ! sh "${ACTION_PATH}/install.sh"; then
+          echo "::error title=Straitjacket could not be installed::The scan did not run. This is an installation failure, not a finding -- see the log above, and set the action's \`token\` input if it mentions rate limiting." >&2
+          exit 1
+        fi
         echo "$STRAITJACKET_INSTALL_DIR" >> "$GITHUB_PATH"
 
     # Inputs reach the script through the environment rather than through

install.sh

@@ -50,21 +50,33 @@ detect_target() {
     esac
 }
 
+# Retry a few times, because a reset connection on the way to a release is
+# not a reason to fail a build. Rate limiting is not retried away -- see the
+# message in `main` -- but a dropped connection usually is.
+RETRY="--retry 3 --retry-delay 2"
+
 # Fetch a URL to stdout, sending credentials only when they were provided.
 fetch() {
+    # shellcheck disable=SC2086
     if [ -n "${GITHUB_TOKEN:-}" ]; then
-        curl -sSfL -H "Authorization: Bearer ${GITHUB_TOKEN}" "$1"
+        curl -sSfL $RETRY -H "Authorization: Bearer ${GITHUB_TOKEN}" "$1"
     else
-        curl -sSfL "$1"
+        curl -sSfL $RETRY "$1"
     fi
 }
 
 # The tag of the most recent release.
 #
 # Parsed out of the API response with sed rather than a JSON library, because
 # the whole point of this script is to run before anything is installed.
+#
+# The response is captured before it is parsed. Piping the fetch straight into
+# sed hides its exit status behind `head`, so a refused request looked exactly
+# like a repository with no releases -- and the message said so, which sent
+# whoever read it looking in the wrong place.
 latest_version() {
-    fetch "${API}/releases/latest" |
+    response=$(fetch "${API}/releases/latest") || return 1
+    printf '%s\n' "$response" |
         sed -n 's/.*"tag_name"[[:space:]]*:[[:space:]]*"\([^"]*\)".*/\1/p' |
         head -n 1
 }
@@ -135,10 +147,12 @@ download_asset() {
     elif [ -n "${GITHUB_TOKEN:-}" ]; then
         asset_api=$(fetch "${API}/releases/tags/${version}" | asset_url "$asset_name")
         [ -n "$asset_api" ] || die "release ${version} has no asset named ${asset_name}"
-        curl -sSfL -H "Authorization: Bearer ${GITHUB_TOKEN}" \
+        # shellcheck disable=SC2086
+        curl -sSfL $RETRY -H "Authorization: Bearer ${GITHUB_TOKEN}" \
             -H "Accept: application/octet-stream" "$asset_api" >"$asset_output"
     else
-        curl -sSfL "${DOWNLOAD}/${version}/${asset_name}" >"$asset_output"
+        # shellcheck disable=SC2086
+        curl -sSfL $RETRY "${DOWNLOAD}/${version}/${asset_name}" >"$asset_output"
     fi
 }
 
@@ -150,8 +164,12 @@ main() {
     target=$(detect_target)
     version=${STRAITJACKET_VERSION:-}
     if [ -z "$version" ]; then
-        version=$(latest_version) ||
-            die "could not read the latest release. Set STRAITJACKET_VERSION, or GITHUB_TOKEN if the repository is private"
+        version=$(latest_version) || die "could not read the latest release.
+  GitHub allows 60 unauthenticated API requests an hour per address, and CI
+  runners share addresses, so this is usually rate limiting rather than a
+  missing release. Set GITHUB_TOKEN -- any valid token raises the limit, and
+  it need not have access to this repository while it is public. Or pin
+  STRAITJACKET_VERSION, which skips the API entirely."
         [ -n "$version" ] || die "no published release found. Set STRAITJACKET_VERSION to install a specific tag"
     fi