Fallback to the base ref if the previous tag cannot be found

The previous tag may not exist on new projects, so just list
the new commits compared to the base ref.

Change-type: patch
Signed-off-by: Kyle Harding <[email protected]>

Author: klutchell

.github/workflows/flowzone.yml

@@ -1509,17 +1509,18 @@ jobs:
 
             // Get the previous version tag
             const previousTag = filteredTags.find(tag => tag.name.match(/^v\d+\.\d+\.\d+/));
+            const head = context.payload.pull_request?.head.sha || context.sha;
+            let base;
 
             if (!previousTag) {
-              core.setFailed('No previous version tag found');
+              const baseRef = context.payload.pull_request?.base.ref;
+              core.warning(`No previous version tag found, using ${baseRef}`);
+              base = baseRef;
+            } else {
+              core.info(`Found previous versioned tag: ${previousTag.name}`);
+              base = previousTag.name;
             }
 
-            console.log('previousTag:', JSON.stringify(previousTag, null, 2));
-            core.setOutput('previousTag', previousTag);
-
-            const base = previousTag.name;
-            const head = context.payload.pull_request?.head.sha || context.sha;
-
             // Get commit history between previous tag and current commit
             const { data: { commits } } = await github.rest.repos.compareCommitsWithBasehead({
               ...context.repo,