Condense code change to avoid repetition

Author: Andy Furniss

src/GitVersionCore/VersionCalculation/BaseVersionCalculator.cs

@@ -61,18 +61,14 @@ public BaseVersion GetBaseVersion()
 
                 FixTheBaseVersionSourceOfMergeMessageStrategyIfReleaseBranchWasMergedAndDeleted(baseVersions);
 
-                Versions maxVersion;
                 if (context.Configuration.VersioningMode == VersioningMode.Mainline)
                 {
-                    maxVersion = baseVersions
+                    baseVersions = baseVersions
                         .Where(b => !b.IncrementedVersion.PreReleaseTag.HasTag())
-                        .Aggregate((v1, v2) => v1.IncrementedVersion > v2.IncrementedVersion ? v1 : v2);
-                }
-                else
-                {
-                    maxVersion = baseVersions.Aggregate((v1, v2) => v1.IncrementedVersion > v2.IncrementedVersion ? v1 : v2);
+                        .ToList();
                 }
 
+                var maxVersion = baseVersions.Aggregate((v1, v2) => v1.IncrementedVersion > v2.IncrementedVersion ? v1 : v2);
                 var matchingVersionsOnceIncremented = baseVersions
                     .Where(b => b.Version.BaseVersionSource != null && b.IncrementedVersion == maxVersion.IncrementedVersion)
                     .ToList();