fix: use Current branch instead of master for LTS comparison

Author: codebytere

lib/prepare_release.js

@@ -443,15 +443,22 @@ class ReleasePreparation {
         `backport-blocked-v${majorVersion}.x`
       ];
 
+      let comparisonBranch = 'master';
       const isSemverMinor = versionComponents.patch === 0;
-      if (isLTS && !isSemverMinor) {
-        excludeLabels.push('semver-minor');
+      if (isLTS) {
+        // Assume current branch corresponds to the tag with highest semver value.
+        const tags = runSync('git' ['tag', '-l', '--sort', '-version:refname']).trim();
+        const highestVersionTag = tags.split('\n')[0];
+        comparisonBranch = `v${semver.coerce(highestVersionTag).major}.x`
+
+        if (!isSemverMinor) {
+          excludeLabels.push('semver-minor');
+        }
       }
 
       branchDiffOptions = [
         stagingBranch,
-        // TODO(codebytere): use Current branch instead of master for LTS
-        'master',
+        comparisonBranch,
         `--exclude-label=${excludeLabels.join(',')}`,
         '--filter-release'
       ];