[Bugfix] CommitsSinceVersionSource decreases upon deleting a merged Release branch

src/GitVersionCore.Tests/IntegrationTests/DevelopScenarios.cs

@@ -222,4 +222,81 @@ public void TagOnHotfixShouldNotAffectDevelop()
             fixture.AssertFullSemver("1.3.0-alpha.2");
         }
     }
+
+    [Test]
+    public void CommitsSinceVersionSourceShouldNotGoDownUponGitFlowReleaseFinish()
+    {
+        var config = new Config
+        {
+            VersioningMode = VersioningMode.ContinuousDeployment
+        };
+
+        using (var fixture = new EmptyRepositoryFixture())
+        {
+            fixture.MakeACommit();
+            fixture.ApplyTag("1.1.0");
+            fixture.BranchTo("develop");
+            fixture.MakeACommit("commit in develop - 1");
+            fixture.AssertFullSemver("1.2.0-alpha.1");
+            fixture.BranchTo("release/1.2.0");
+            fixture.AssertFullSemver("1.2.0-beta.1+0");
+            fixture.Checkout("develop");
+            fixture.MakeACommit("commit in develop - 2");
+            fixture.MakeACommit("commit in develop - 3");
+            fixture.MakeACommit("commit in develop - 4");
+            fixture.MakeACommit("commit in develop - 5");
+            fixture.AssertFullSemver("1.3.0-alpha.4");
+            fixture.Checkout("release/1.2.0");
+            fixture.MakeACommit("commit in release/1.2.0 - 1");
+            fixture.MakeACommit("commit in release/1.2.0 - 2");
+            fixture.MakeACommit("commit in release/1.2.0 - 3");
+            fixture.AssertFullSemver("1.2.0-beta.1+3");
+            fixture.Checkout("master");
+            fixture.MergeNoFF("release/1.2.0");
+            fixture.ApplyTag("1.2.0");
+            fixture.Checkout("develop");
+            fixture.MergeNoFF("release/1.2.0");
+            fixture.MakeACommit("commit in develop - 6");
+            fixture.AssertFullSemver("1.3.0-alpha.9");
+            fixture.SequenceDiagram.Destroy("release/1.2.0");
+            fixture.Repository.Branches.Remove("release/1.2.0");
+
+            var expectedFullSemVer = "1.3.0-alpha.9";
+            fixture.AssertFullSemver(config, expectedFullSemVer);
+        }
+    }
+
+    [Test]
+    public void CommitsSinceVersionSourceShouldNotGoDownUponMergingFeatureOnlyToDevelop()
+    {
+        var config = new Config
+        {
+            VersioningMode = VersioningMode.ContinuousDeployment
+        };
+
+        using (var fixture = new EmptyRepositoryFixture())
+        {
+            fixture.MakeACommit("commit in master - 1");
+            fixture.ApplyTag("1.1.0");
+            fixture.BranchTo("develop");
+            fixture.MakeACommit("commit in develop - 1");
+            fixture.AssertFullSemver("1.2.0-alpha.1");
+            fixture.BranchTo("release/1.2.0");
+            fixture.MakeACommit("commit in release - 1");
+            fixture.MakeACommit("commit in release - 2");
+            fixture.MakeACommit("commit in release - 3");
+            fixture.AssertFullSemver("1.2.0-beta.1+3");
+            fixture.ApplyTag("1.2.0");
+            fixture.Checkout("develop");
+            fixture.MakeACommit("commit in develop - 2");
+            fixture.AssertFullSemver("1.3.0-alpha.1");
+            fixture.MergeNoFF("release/1.2.0");
+            fixture.AssertFullSemver("1.3.0-alpha.5");
+            fixture.SequenceDiagram.Destroy("release/1.2.0");
+            fixture.Repository.Branches.Remove("release/1.2.0");
+
+            var expectedFullSemVer = "1.3.0-alpha.5";
+            fixture.AssertFullSemver(config, expectedFullSemVer);
+        }
+    }
 }

src/GitVersionCore.Tests/IntegrationTests/ReleaseBranchScenarios.cs

@@ -51,7 +51,7 @@ public void NoMergeBacksToDevelopInCaseThereAreChangesInReleaseBranch()
             fixture.Repository.MakeACommit();
             fixture.Repository.Branches.Remove("release/1.0.0");
 
-            fixture.AssertFullSemver("1.1.0-alpha.2");
+            fixture.AssertFullSemver("1.1.0-alpha.3");
         }
     }
 

src/GitVersionCore/VersionCalculation/BaseVersionCalculator.cs

@@ -1,7 +1,9 @@
-namespace GitVersion.VersionCalculation
+namespace GitVersion.VersionCalculation
 {
     using System;
+    using System.Collections.Generic;
     using System.Linq;
+    using System.Text.RegularExpressions;
     using GitVersion.VersionCalculation.BaseVersionCalculators;
 
     public class BaseVersionCalculator : IBaseVersionCalculator
@@ -37,13 +39,15 @@ public BaseVersion GetBaseVersion(GitVersionContext context)
 
                         return true;
                     })
-                    .Select(v => new
+                    .Select(v => new Versions
                     {
                         IncrementedVersion = MaybeIncrement(context, v),
                         Version = v
                     })
                     .ToList();
 
+                FixTheBaseVersionSourceOfMergeMessageStrategyIfReleaseBranchWasMergedAndDeleted
+                    (context, baseVersions);
                 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)
@@ -92,5 +96,46 @@ public static SemanticVersion MaybeIncrement(GitVersionContext context, BaseVers
 
             return version.SemanticVersion;
         }
+
+        private void FixTheBaseVersionSourceOfMergeMessageStrategyIfReleaseBranchWasMergedAndDeleted(
+            GitVersionContext context, List<Versions> baseVersions)
+        {
+            if (!ReleaseBranchExistsInRepo(context))
+            {
+                foreach (var baseVersion in baseVersions)
+                {
+                    if (baseVersion.Version.Source.Contains(
+                        MergeMessageBaseVersionStrategy.MergeMessageStrategyPrefix)
+                        && baseVersion.Version.Source.Contains("Merge branch")
+                        && baseVersion.Version.Source.Contains("release"))
+                    {
+                        var parents = baseVersion.Version.BaseVersionSource.Parents.ToList();
+                        baseVersion.Version = new BaseVersion(
+                            context,
+                            baseVersion.Version.Source,
+                            baseVersion.Version.ShouldIncrement,
+                            baseVersion.Version.SemanticVersion,
+                            context.Repository.ObjectDatabase.FindMergeBase(parents[0], parents[1]),
+                            baseVersion.Version.BranchNameOverride);
+                    }
+                }
+            }
+        }
+
+        private bool ReleaseBranchExistsInRepo(GitVersionContext context)
+        {
+            var releaseBranchConfig = context.FullConfiguration.Branches
+                .Where(b => b.Value.IsReleaseBranch == true)
+                .ToList();
+            var releaseBranches = context.Repository.Branches
+                    .Where(b => releaseBranchConfig.Any(c => Regex.IsMatch(b.FriendlyName, c.Value.Regex)));
+            return releaseBranches.Any();
+        }
+
+        private class Versions
+        {
+            public SemanticVersion IncrementedVersion { get; set; }
+            public BaseVersion Version { get; set; }
+        }
     }
-}
+}

src/GitVersionCore/VersionCalculation/BaseVersionCalculators/MergeMessageBaseVersionStrategy.cs

@@ -26,14 +26,16 @@ public override IEnumerable<BaseVersion> GetVersions(GitVersionContext context)
                         var shouldIncrement = !context.Configuration.PreventIncrementForMergedBranchVersion;
                         return new[]
                         {
-                            new BaseVersion(context, $"Merge message '{c.Message.Trim()}'", shouldIncrement, mergeMessage.Version, c, null)
+                            new BaseVersion(context, $"{MergeMessageStrategyPrefix} '{c.Message.Trim()}'", shouldIncrement, mergeMessage.Version, c, null)
                         };
                     }
                     return Enumerable.Empty<BaseVersion>();
                 }).ToList();
             return baseVersions;
         }
 
+        public static readonly string MergeMessageStrategyPrefix = "Merge message";
+
         static bool TryParse(Commit mergeCommit, GitVersionContext context, out MergeMessage mergeMessage)
         {
             mergeMessage = Inner(mergeCommit, context);