ci(security): hold API responses in a file instead of piping them onward

Semgrep blocks on gha-curl-pipe-shell, and it is pointing at the publish step
added an hour ago. The rule exists for `curl https://…/install.sh | bash`:
remote content reaching an interpreter. What this actually did was pipe a JSON
response into a python3 -c inline script -- the interpreter and its program both
live in the workflow file, and the server only ever supplied data.

A false positive, then, but the rule cannot see the difference between an
interpreter reading a program from stdin and one reading data, and neither can
the next person to read the step. Responses go to a file and are read from
there. Same shape as the finding suggests, and worth having anyway: a response
that is on disk can be looked at when a call misbehaves, instead of vanishing
into a pipe.

Verified by falsification rather than by a green run: the same ruleset against
the previous revision of this file reports 1 blocking finding, against this one
zero. Without that check a passing scan only proves the rule was not loaded.

.gitea/workflows/release.yml

@@ -174,28 +174,43 @@ jobs:
           api="${GITHUB_API_URL}/repos/${GITHUB_REPOSITORY}"
           auth="Authorization: token ${GITEA_TOKEN}"
 
-          # Existing release for this tag, or create one.
-          rel_id="$(curl -sf -H "$auth" "$api/releases/tags/${TAG_NAME}" \
-              | python3 -c 'import sys,json; print(json.load(sys.stdin).get("id",""))' 2>/dev/null || true)"
+          # Responses land in a file before anything reads them, rather than
+          # being piped straight into an interpreter. The interpreter is inline
+          # either way and the server only ever supplies data, but a scanner
+          # cannot tell those apart from curl-pipe-shell -- and holding the
+          # response makes it inspectable when a call misbehaves.
+          get_release_id() {
+              if curl -sf -H "$auth" "$api/releases/tags/${TAG_NAME}" -o release.json; then
+                  python3 -c 'import json; print(json.load(open("release.json")).get("id",""))'
+              fi
+          }
+
+          rel_id="$(get_release_id || true)"
 
           if [ -z "$rel_id" ]; then
-              payload="$(python3 -c '
-          import json, os, sys
+              python3 - <<'PYCREATE' > create.json
+          import json, os
           body = open("release-body.md", encoding="utf-8").read()
-          json.dump({"tag_name": os.environ["TAG_NAME"], "name": os.environ["TAG_NAME"],
-                     "body": body, "draft": False, "prerelease": False}, sys.stdout)
-          ')"
-              rel_id="$(printf '%s' "$payload" \
-                  | curl -sf -X POST -H "$auth" -H "Content-Type: application/json" -d @- "$api/releases" \
-                  | python3 -c 'import sys,json; print(json.load(sys.stdin)["id"])')"
+          print(json.dumps({
+              "tag_name": os.environ["TAG_NAME"],
+              "name": os.environ["TAG_NAME"],
+              "body": body,
+              "draft": False,
+              "prerelease": False,
+          }))
+          PYCREATE
+              curl -sf -X POST -H "$auth" -H "Content-Type: application/json" \
+                  -d @create.json "$api/releases" -o created.json
+              rel_id="$(python3 -c 'import json; print(json.load(open("created.json"))["id"])')"
               echo "Created release $rel_id for ${TAG_NAME}"
           else
               echo "Reusing release $rel_id for ${TAG_NAME}"
           fi
 
-          # Drop a same-named asset from an earlier attempt, or the upload 409s.
-          old_id="$(curl -sf -H "$auth" "$api/releases/${rel_id}/assets" \
-              | python3 -c 'import sys,json; print(next((a["id"] for a in json.load(sys.stdin) if a["name"]=="latest.zip"), ""))' 2>/dev/null || true)"
+          # A same-named asset from an earlier attempt has to go, or the upload
+          # collides with it. This is the state a recovery run finds.
+          curl -sf -H "$auth" "$api/releases/${rel_id}/assets" -o assets.json
+          old_id="$(python3 -c 'import json; print(next((a["id"] for a in json.load(open("assets.json")) if a["name"]=="latest.zip"), ""))')"
           if [ -n "$old_id" ]; then
               curl -sf -X DELETE -H "$auth" "$api/releases/${rel_id}/assets/${old_id}"
               echo "Replaced existing latest.zip (asset $old_id)"
@@ -203,5 +218,5 @@ jobs:
 
           curl -sf -X POST -H "$auth" \
               -F "attachment=@${ZIP_PATH};filename=latest.zip" \
-              "$api/releases/${rel_id}/assets?name=latest.zip" \
-              | python3 -c 'import sys,json; a=json.load(sys.stdin); print("Attached", a["name"], a["size"], "bytes")'
+              "$api/releases/${rel_id}/assets?name=latest.zip" -o uploaded.json
+          python3 -c 'import json; a=json.load(open("uploaded.json")); print("Attached", a["name"], a["size"], "bytes")'