Adding Merge Commit Version Strategy

src/GitVersion.Core/Configuration/ConfigurationConstants.cs

@@ -19,7 +19,8 @@ internal static class ConfigurationConstants
         VersionStrategies.MergeMessage,
         VersionStrategies.TaggedCommit,
         VersionStrategies.TrackReleaseBranches,
-        VersionStrategies.VersionInBranchName
+        VersionStrategies.VersionInBranchName,
+        VersionStrategies.MergeCommit
     ];
     public const string DefaultAssemblyInformationalFormat = "{InformationalVersion}";
     public const string DefaultCommitDateFormat = "yyyy-MM-dd";

src/GitVersion.Core/PublicAPI.Shipped.txt

@@ -680,6 +680,7 @@ GitVersion.VersionCalculation.VersionStrategies
 GitVersion.VersionCalculation.VersionStrategies.ConfiguredNextVersion = 2 -> GitVersion.VersionCalculation.VersionStrategies
 GitVersion.VersionCalculation.VersionStrategies.Fallback = 1 -> GitVersion.VersionCalculation.VersionStrategies
 GitVersion.VersionCalculation.VersionStrategies.Mainline = 64 -> GitVersion.VersionCalculation.VersionStrategies
+GitVersion.VersionCalculation.VersionStrategies.MergeCommit = 128 -> GitVersion.VersionCalculation.VersionStrategies
 GitVersion.VersionCalculation.VersionStrategies.MergeMessage = 4 -> GitVersion.VersionCalculation.VersionStrategies
 GitVersion.VersionCalculation.VersionStrategies.None = 0 -> GitVersion.VersionCalculation.VersionStrategies
 GitVersion.VersionCalculation.VersionStrategies.TaggedCommit = 8 -> GitVersion.VersionCalculation.VersionStrategies

src/GitVersion.Core/VersionCalculation/VersionSearchStrategies/MergeCommitVersionStrategy.cs

@@ -0,0 +1,97 @@
+using GitVersion.Common;
+using GitVersion.Configuration;
+using GitVersion.Core;
+using GitVersion.Extensions;
+using GitVersion.Git;
+using GitVersion.Logging;
+
+namespace GitVersion.VersionCalculation;
+
+/// <summary>
+/// Version is extracted from older merge commits.
+/// BaseVersionSource is the commit where the message was found.
+/// </summary>
+internal sealed class MergeCommitVersionStrategy(ILog log, Lazy<GitVersionContext> contextLazy,
+    IRepositoryStore repositoryStore, IIncrementStrategyFinder incrementStrategyFinder,     IEffectiveBranchConfigurationFinder effectiveBranchConfigurationFinder,
+    ITaggedSemanticVersionRepository taggedSemanticVersionRepository
+    )
+    : IVersionStrategy
+{
+    private readonly ILog log = log.NotNull();
+    private readonly Lazy<GitVersionContext> contextLazy = contextLazy.NotNull();
+    private readonly IRepositoryStore repositoryStore = repositoryStore.NotNull();
+    private readonly IIncrementStrategyFinder incrementStrategyFinder = incrementStrategyFinder.NotNull();
+    private readonly IEffectiveBranchConfigurationFinder effectiveBranchConfigurationFinder = effectiveBranchConfigurationFinder.NotNull();
+    private readonly ITaggedSemanticVersionRepository taggedSemanticVersionRepository = taggedSemanticVersionRepository.NotNull();
+
+    private GitVersionContext Context => contextLazy.Value;
+
+    public IEnumerable<BaseVersion> GetBaseVersions(EffectiveBranchConfiguration configuration)
+    {
+        configuration.NotNull();
+
+        if (!Context.Configuration.VersionStrategy.HasFlag(VersionStrategies.MergeCommit))
+        {
+            yield break;
+        }
+
+        var taggedCommits = this.taggedSemanticVersionRepository.GetTaggedSemanticVersions(
+            tagPrefix: Context.Configuration.TagPrefixPattern,
+            format: Context.Configuration.SemanticVersionFormat,
+            ignore: Context.Configuration.Ignore
+        );
+        var previousVersion = new SemanticVersion(0, 0, 0);
+
+        // Must Loop In Reverse To Ensure Correct Version Calculation
+        foreach (var commit in configuration.Value.Ignore.Filter(Context.CurrentBranchCommits.ToArray()).Reverse())
+        {
+            if (taggedCommits.Contains(commit))
+            {
+                this.log.Debug($"Found tagged commit {commit}, adjusting previous version.");
+                previousVersion = taggedCommits[commit].First().Value;
+            }
+            if (!commit.IsMergeCommit())
+            {
+                continue;
+            }
+
+            // Using Merge Message Since The Formats Are Identical
+            if (!MergeMessage.TryParse(commit, Context.Configuration, out var mergeMessage))
+            {
+                continue;
+            }
+
+            this.log.Info($"Found commit [{commit}] matching merge message format: {mergeMessage.FormatName}");
+
+            var currentBranch = this.repositoryStore.GetTargetBranch(mergeMessage.MergedBranch!.Friendly);
+            var branchConfiguration = this.effectiveBranchConfigurationFinder.GetConfigurations(currentBranch, Context.Configuration).First();
+            var baseVersionSource = this.repositoryStore.FindMergeBase(commit.Parents[0], commit.Parents[1]);
+
+            var label = branchConfiguration.Value.GetBranchSpecificLabel(mergeMessage.MergedBranch!.Friendly, "");
+            var increment = this.incrementStrategyFinder.DetermineIncrementedField(
+                    currentCommit: commit,
+                    baseVersionSource: baseVersionSource,
+                    shouldIncrement: true,
+                    configuration: branchConfiguration.Value,
+                    label: label
+                );
+
+            yield return new BaseVersion($"Merge Commit From '{mergeMessage.MergedBranch?.Friendly}'", previousVersion
+            )
+            {
+                Operator = new()
+                {
+                    Increment = increment,
+                    ForceIncrement = false,
+                    Label = label
+                }
+            };
+
+            previousVersion = previousVersion.Increment(
+                increment,
+                label,
+                true
+            );
+        }
+    }
+}

src/GitVersion.Core/VersionCalculation/VersionStrategies.cs

@@ -10,5 +10,6 @@ public enum VersionStrategies
     TaggedCommit = 8,
     TrackReleaseBranches = 16,
     VersionInBranchName = 32,
-    Mainline = 64
+    Mainline = 64,
+    MergeCommit = 128
 }