feat(ci): prune release assets outside the newest two tags (#52)

Gitea has no release-asset retention, so every v* tag kept its full
cross-platform binary set forever — 31 tags had accumulated 1.8 GB on the
production host disk. Nothing consumes an old asset: CI takes the Crucible
binary from the Nix flake, and every deleted file is reproducible from its tag.

scripts/prune-release-assets.sh lists every release page, sorts by creation
date, skips the newest two published releases, and deletes the remaining
releases' attachments. Two rather than one so a release in flight never leaves
the previous download broken. Drafts never consume a keep slot. Releases, tags,
source archives and release notes are untouched.

Nothing is excluded — SHA256SUMS and the wrappers go with the binaries: the
checksums are only meaningful next to the files they cover, and the consumer
drift-check reads the wrappers from the latest release, which stays complete.

The step is best-effort: a stale asset is cheaper than a blocked publish, so
API failures warn and the step carries continue-on-error.

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>

tests/prune-release-assets.sh

@@ -0,0 +1,78 @@
+#!/usr/bin/env bash
+# Contract for scripts/prune-release-assets.sh, driven by a stub curl on PATH:
+# only assets of releases outside the keep window go, the window is decided by
+# release date rather than response order, drafts never consume a keep slot,
+# releases and tags stay, and an API failure never fails the run.
+set -euo pipefail
+
+repo_root="$(cd "$(dirname "${BASH_SOURCE[0]}")/.." && pwd)"
+script="$repo_root/scripts/prune-release-assets.sh"
+tmp="$(mktemp -d)"
+trap 'rm -rf "$tmp"' EXIT
+
+# Stub curl: one short page of releases, deliberately out of date order and
+# with a draft that is newer than every published release. Each release embeds
+# two assets. Every request is appended to $CALLS for the assertions below.
+mkdir -p "$tmp/bin"
+cat >"$tmp/bin/curl" <<'STUB'
+#!/usr/bin/env bash
+url="${!#}"
+printf '%s\n' "$*" >>"$CALLS"
+rel() { printf '{"id":%s,"created_at":"%s","draft":%s,"assets":[{"id":%s01},{"id":%s02}]}' "$1" "$2" "$3" "$1" "$1"; }
+case "$url" in
+  *releases\?*)
+    [[ "${FAIL_LIST:-0}" == 1 ]] && exit 22
+    printf '[%s,%s,%s,%s,%s]\n' \
+      "$(rel 12 2024-01-02T00:00:00Z false)" \
+      "$(rel 10 2024-01-04T00:00:00Z false)" \
+      "$(rel 9  2024-06-01T00:00:00Z true)" \
+      "$(rel 13 2024-01-01T00:00:00Z false)" \
+      "$(rel 11 2024-01-03T00:00:00Z false)"
+    ;;
+  */assets/*) [[ "${FAIL_DELETE:-0}" == 1 ]] && exit 22 ;;
+esac
+exit 0
+STUB
+chmod +x "$tmp/bin/curl"
+export PATH="$tmp/bin:$PATH" API=https://git.example/api/v1/repos/o/r TOKEN=t
+
+run() { CALLS="$tmp/calls" bash "$script" >"$tmp/out" 2>"$tmp/err"; }
+
+# Default keep=2: the two newest published releases (10, 11) stay whole, the
+# older two (12, 13) lose their assets, and the newer draft is ignored.
+: >"$tmp/calls"; run
+deletes="$(grep -c -- '-X DELETE' "$tmp/calls" || true)"
+[[ "$deletes" == 4 ]] || { echo "expected 4 asset deletes, got $deletes" >&2; exit 1; }
+grep -q 'assets/1201' "$tmp/calls" && grep -q 'assets/1302' "$tmp/calls" || {
+  echo "expected assets of releases 12 and 13 to be deleted" >&2; exit 1; }
+if grep -q 'releases/10/assets/\|releases/11/assets/' "$tmp/calls"; then
+  echo "kept releases lost assets" >&2; exit 1
+fi
+if grep -q 'releases/9/assets/' "$tmp/calls"; then
+  echo "a draft release was pruned" >&2; exit 1
+fi
+# A release or tag must never be deleted, only attachments under /assets/.
+if grep -- '-X DELETE' "$tmp/calls" | grep -qv '/assets/'; then
+  echo "a non-asset DELETE was issued" >&2; exit 1
+fi
+# A short page ends the sweep: no second page, so a server ignoring `page`
+# cannot spin the job until the job timeout.
+[[ "$(grep -c 'releases?' "$tmp/calls")" == 1 ]] || {
+  echo "a short release page did not end the sweep" >&2; exit 1; }
+
+# KEEP=4 covers every published release: nothing to delete.
+: >"$tmp/calls"; KEEP=4 run
+if grep -q -- '-X DELETE' "$tmp/calls"; then echo "KEEP=4 still deleted" >&2; exit 1; fi
+
+# Failures are warnings, never a non-zero exit.
+: >"$tmp/calls"; FAIL_DELETE=1 run || { echo "delete failure failed the run" >&2; exit 1; }
+grep -q 'failed' "$tmp/err" || { echo "delete failure was not warned about" >&2; exit 1; }
+
+: >"$tmp/calls"; FAIL_LIST=1 run || { echo "listing failure failed the run" >&2; exit 1; }
+grep -q 'listing releases failed' "$tmp/err" || {
+  echo "listing failure was not warned about" >&2; exit 1; }
+if grep -q -- '-X DELETE' "$tmp/calls"; then
+  echo "deleted assets despite an unreadable release list" >&2; exit 1
+fi
+
+echo "prune-release-assets: prunes by release date outside the keep window, ignores drafts, never deletes a release, never fails the build"

tests/workflow-contract.sh

@@ -46,6 +46,8 @@ grep -Fqx '  releases: write' "$release"
 grep -Fqx '    timeout-minutes: 30' "$release"
 [[ "$(grep -Fc "$checkout" "$release")" -eq 1 ]]
 grep -Fq 'secrets.GITEA_TOKEN' "$release"
+grep -Fq 'scripts/prune-release-assets.sh' "$release"
+grep -Fq 'continue-on-error: true' "$release"
 if grep -Fq 'secrets.GITHUB_TOKEN' "$release"; then
   echo "workflow-contract: release uses the GitHub token alias" >&2
   exit 1