Make release script more robust and send user agent

.github/workflows/trigger-release/trigger-release.py

@@ -1,3 +1,4 @@
+import sys
 import toml
 import requests
 import subprocess
@@ -6,16 +7,23 @@
 crate_version = cargo_toml["workspace"]["package"]["version"]
 print("Detected crate version " + crate_version)
 
+# crates.io enforces a data-access policy that requires a descriptive
+# User-Agent with contact info; requests without one get rejected, which
+# previously made this script misclassify already-published versions as
+# unreleased. See https://crates.io/data-access.
+headers = {
+    "User-Agent": "bootloader-release-ci (https://github.com/rust-osdev/bootloader)"
+}
 api_url = "https://crates.io/api/v1/crates/bootloader/" + crate_version
-released_version = requests.get(api_url).json()
+response = requests.get(api_url, headers=headers)
 
-if "version" in released_version:
-    version = released_version["version"]
+if response.status_code == 200 and "version" in response.json():
+    version = response.json()["version"]
     assert (version["crate"] == "bootloader")
     assert (version["num"] == crate_version)
     print("Version " + crate_version + " already exists on crates.io")
 
-else:
+elif response.status_code == 404:
     print("Could not find version " + crate_version +
           " on crates.io; creating a new release")
 
@@ -33,6 +41,26 @@
         "-F", "draft=false", "-F", "prerelease=false", "-F", "generate_release_notes=false",
     ]
     print("  Running `" + ' '.join(command) + '`')
-    subprocess.run(command, check=True)
+    result = subprocess.run(command, capture_output=True, text=True)
+    sys.stdout.write(result.stdout)
+    sys.stderr.write(result.stderr)
+    if result.returncode != 0:
+        # A release for this tag may already exist (e.g. the version was
+        # published on crates.io but the crates.io check briefly failed, or
+        # this workflow is being re-run). Treat that as a no-op instead of a
+        # hard failure; fail loudly on any other error.
+        if "already_exists" in result.stdout or "already_exists" in result.stderr:
+            print(f"  Release {tag_name} already exists; nothing to do")
+        else:
+            raise SystemExit(result.returncode)
+    else:
+        print("  Done")
 
-    print("  Done")
+else:
+    # Any other response (rate limiting, data-access policy rejection, 5xx,
+    # etc.) is ambiguous: we can't tell whether the version is published.
+    # Fail loudly rather than guessing and attempting to re-create a release.
+    raise SystemExit(
+        f"Unexpected response from crates.io (HTTP {response.status_code}): "
+        f"{response.text}"
+    )