fix(diff): fix prerelease to stable version diff logic (#755)

Refactored version diff logic to handle transitions from prerelease
versions to stable versions correctly for major/minor/patch version
bumps.

Closes #606

---------

Co-authored-by: berkay.daglar <berkay.daglar@v-count.com>

Author: eminberkayd

functions/diff.js

@@ -27,20 +27,13 @@ const diff = (version1, version2) => {
       return 'major'
     }
 
-    // Otherwise it can be determined by checking the high version
-
-    if (highVersion.patch) {
-      // anything higher than a patch bump would result in the wrong version
+    // If the main part has no difference
+    if (lowVersion.compareMain(highVersion) === 0) {
+      if (lowVersion.minor && !lowVersion.patch) {
+        return 'minor'
+      }
       return 'patch'
     }
-
-    if (highVersion.minor) {
-      // anything higher than a minor bump would result in the wrong version
-      return 'minor'
-    }
-
-    // bumping major/minor/patch all have same result
-    return 'major'
   }
 
   // add the `pre` prefix if we are going to a prerelease version

test/functions/diff.js

@@ -34,6 +34,13 @@ test('diff versions test', (t) => {
     ['1.0.0-1', '2.0.0-1', 'premajor'],
     ['1.0.0-1', '1.1.0-1', 'preminor'],
     ['1.0.0-1', '1.0.1-1', 'prepatch'],
+    ['1.7.2-1', '1.8.1', 'minor'],
+    ['1.1.1-pre', '2.1.1-pre', 'premajor'],
+    ['1.1.1-pre', '2.1.1', 'major'],
+    ['1.2.3-1', '1.2.3', 'patch'],
+    ['1.4.0-1', '2.3.5', 'major'],
+    ['1.6.1-5', '1.7.2', 'minor'],
+    ['2.0.0-1', '2.1.1', 'major'],
   ].forEach((v) => {
     const version1 = v[0]
     const version2 = v[1]