Strip SSH signatures from tag annotation bodies

Closes #31

src/git.js

@@ -1,5 +1,8 @@
 import { exec, getExecOutput } from "@actions/exec";
 
+const SIGNATURE_PATTERN =
+  /-----BEGIN (\w+) SIGNATURE-----.*-----END \1 SIGNATURE-----/;
+
 export async function determineRef({ group, info, silent = false }) {
   return group("Determining the current Git ref", async () => {
     const { stdout } = await getExecOutput(
@@ -78,8 +81,20 @@ export async function readTagAnnotation({ group, silent = false, tag }) {
       }
     );
 
-    return [true, tagSubject.trim(), tagBody.trim()];
+    return [true, tagSubject.trim(), trimTagBody(tagBody)];
   } catch {
     return [false, "", ""];
   }
 }
+
+/**
+ * This function is unfortunately necessary because the version of Git on the
+ * Node.js Docker base image that I use is too old to understand SSH signatures,
+ * and does not automatically remove them from tag annotation bodies.
+ *
+ * Once the Git version used on the Node.js Docker image is 2.34.0 or greater,
+ * this function can be removed, and replaced with a simple trim operation.
+ */
+function trimTagBody(tagBody) {
+  return tagBody.replace(SIGNATURE_PATTERN, "").trim();
+}