#1754 Allow head to move when switching branches for dynamic repositories

Author: GeertvanHorrik

src/GitVersionCore.Tests/Extensions/ExtensionMethodsTests.cs

@@ -0,0 +1,22 @@
+using GitVersion;
+using NUnit.Framework;
+
+namespace GitVersionCore.Tests
+{
+    [TestFixture]
+    public class ExtensionMethodsTests
+    {
+        [TestCase("develop", "develop", true)]
+        [TestCase("develop", "master", false)]
+        [TestCase("/refs/head/develop", "develop", true)]
+        [TestCase("/refs/head/master", "develop", false)]
+        [TestCase("superdevelop", "develop", false)]
+        [TestCase("/refs/head/superdevelop", "develop", false)]
+        public void TheIsBranchMethod(string input1, string input2, bool expectedOutput)
+        {
+            var actualOutput = input1.IsBranch(input2);
+
+            Assert.AreEqual(expectedOutput, actualOutput);
+        }
+    }
+}

src/GitVersionCore/Extensions/ExtensionMethods.cs

@@ -7,6 +7,23 @@ namespace GitVersion
 
     static class ExtensionMethods
     {
+        public static bool IsBranch(this string branchName, string branchNameToCompareAgainst)
+        {
+            // "develop" == "develop"
+            if (string.Equals(branchName, branchNameToCompareAgainst, StringComparison.OrdinalIgnoreCase))
+            {
+                return true;
+            }
+
+            // "refs/head/develop" == "develop"
+            if (branchName.EndsWith($"/{branchNameToCompareAgainst}", StringComparison.OrdinalIgnoreCase))
+            {
+                return true;
+            }
+
+            return false;
+        }
+
         public static void AppendLineFormat(this StringBuilder stringBuilder, string format, params object[] args)
         {
             stringBuilder.AppendFormat(format, args);

src/GitVersionCore/GitVersionContext.cs

@@ -1,4 +1,4 @@
-namespace GitVersion
+namespace GitVersion
 {
     using LibGit2Sharp;
     using System;
@@ -163,7 +163,9 @@ private static Branch GetTargetBranch(IRepository repository, string targetBranc
             {
                 // There are some edge cases where HEAD is not pointing to the desired branch.
                 // Therefore it's important to verify if 'currentBranch' is indeed the desired branch.
-                if (desiredBranch.CanonicalName != targetBranch)
+
+                // CanonicalName can be "refs/heads/develop", so we need to check for "/{TargetBranch}" as well
+                if (!desiredBranch.CanonicalName.IsBranch(targetBranch))
                 {
                     // In the case where HEAD is not the desired branch, try to find the branch with matching name
                     desiredBranch = repository?.Branches?

src/GitVersionCore/Helpers/GitRepositoryHelper.cs

@@ -15,8 +15,10 @@ public static void NormalizeGitDirectory(string gitDirectory, AuthenticationInfo
         {
             using (var repo = new Repository(gitDirectory))
             {
-                // Need to unsure the HEAD does not move, this is essentially a BugCheck
+                // Need to ensure the HEAD does not move, this is essentially a BugCheck
                 var expectedSha = repo.Head.Tip.Sha;
+                var expectedBranchName = repo.Head.CanonicalName;
+
                 try
                 {
                     var remote = EnsureOnlyOneRemoteIsDefined(repo);
@@ -36,6 +38,20 @@ public static void NormalizeGitDirectory(string gitDirectory, AuthenticationInfo
                     EnsureLocalBranchExistsForCurrentBranch(repo, remote, currentBranch);
                     CreateOrUpdateLocalBranchesFromRemoteTrackingOnes(repo, remote.Name);
 
+                    // Bug fix for https://github.com/GitTools/GitVersion/issues/1754, head maybe have been changed
+                    // if this is a dynamic repository. But only allow this in case the branches are different (branch switch)
+                    if (expectedSha != repo.Head.Tip.Sha &&
+                        !expectedBranchName.IsBranch(currentBranch))
+                    {
+                        var newExpectedSha = repo.Head.Tip.Sha;
+                        var newExpectedBranchName = repo.Head.CanonicalName;
+
+                        Logger.WriteInfo($"Head has moved from '{expectedBranchName} | {expectedSha}' => '{newExpectedBranchName} | {newExpectedSha}', allowed since this is a dynamic repository");
+
+                        expectedSha = newExpectedSha;
+                        expectedBranchName = newExpectedBranchName;
+                    }
+
                     var headSha = repo.Refs.Head.TargetIdentifier;
 
                     if (!repo.Info.IsHeadDetached)