Guess when there are two branches pointing at the same commit. Trying to go for most stable branch

Still cases where it will fail build, but this should fix the most common cases

Author: JakeGinnivan

GitVersionCore.Tests/Fixtures/RemoteRepositoryFixture.cs

@@ -20,6 +20,14 @@ public RemoteRepositoryFixture(Config configuration)
         CloneRepository();
     }
 
+    /// <summary>
+    /// Simulates running on build server
+    /// </summary>
+    public void InitialiseRepo()
+    {
+        new GitPreparer(null, null, new Authentication(), null, false, LocalRepositoryPath).Initialise(true);
+    }
+
     static IRepository CreateNewRepository(string path)
     {
         LibGit2Sharp.Repository.Init(path);

GitVersionCore.Tests/GitVersionCore.Tests.csproj

@@ -85,6 +85,7 @@
     <Compile Include="Fixtures\BaseGitFlowRepositoryFixture.cs" />
     <Compile Include="GitVersionContextTests.cs" />
     <Compile Include="Helpers\DirectoryHelper.cs" />
+    <Compile Include="IntegrationTests\OtherScenarios.cs" />
     <Compile Include="IntegrationTests\PullRequestScenarios.cs" />
     <Compile Include="IntegrationTests\RemoteRepositoryScenarios.cs" />
     <Compile Include="IntegrationTests\DevelopScenarios.cs" />

GitVersionCore.Tests/IntegrationTests/OtherScenarios.cs

@@ -0,0 +1,53 @@
+namespace GitVersionCore.Tests.IntegrationTests
+{
+    using System.Linq;
+    using GitVersion;
+    using LibGit2Sharp;
+    using NUnit.Framework;
+
+    [TestFixture]
+    public class OtherScenarios
+    {
+        // This is an attempt to automatically resolve the issue where you cannot build
+        // when multiple branches point at the same commit
+        // Current implementation favors master, then branches without - or / in their name
+
+        [Test]
+        public void DoNotBlowUpWhenMasterAndDevelopPointAtSameCommit()
+        {
+            using (var fixture = new RemoteRepositoryFixture(new Config()))
+            {
+                fixture.Repository.MakeACommit();
+                fixture.Repository.MakeATaggedCommit("1.0.0");
+                fixture.Repository.MakeACommit();
+                fixture.Repository.CreateBranch("develop");
+
+                fixture.LocalRepository.Network.Fetch(fixture.LocalRepository.Network.Remotes.First());
+                fixture.LocalRepository.Checkout(fixture.Repository.Head.Tip);
+                fixture.LocalRepository.Branches.Remove("master");
+                fixture.InitialiseRepo();
+                fixture.AssertFullSemver("1.0.1+1");
+            }
+        }
+
+        [Test]
+        public void DoNotBlowUpWhenDevelopAndFeatureBranchPointAtSameCommit()
+        {
+            using (var fixture = new RemoteRepositoryFixture(new Config()))
+            {
+                fixture.Repository.MakeACommit();
+                fixture.Repository.CreateBranch("develop").Checkout();
+                fixture.Repository.MakeACommit();
+                fixture.Repository.MakeATaggedCommit("1.0.0");
+                fixture.Repository.MakeACommit();
+                fixture.Repository.CreateBranch("feature/someFeature");
+
+                fixture.LocalRepository.Network.Fetch(fixture.LocalRepository.Network.Remotes.First());
+                fixture.LocalRepository.Checkout(fixture.Repository.Head.Tip);
+                fixture.LocalRepository.Branches.Remove("master");
+                fixture.InitialiseRepo();
+                fixture.AssertFullSemver("1.1.0-unstable.1");
+            }
+        }
+    }
+}

GitVersionCore/BuildServers/GitHelper.cs

@@ -50,12 +50,33 @@ public static void NormalizeGitDirectory(string gitDirectory, Authentication aut
 
                 if (localBranchesWhereCommitShaIsHead.Count > 1)
                 {
-                    var names = string.Join(", ", localBranchesWhereCommitShaIsHead.Select(r => r.CanonicalName));
-                    var message = string.Format("Found more than one local branch pointing at the commit '{0}'. Unable to determine which one to use ({1}).", headSha, names);
-                    throw new WarningException(message);
+                    var branchNames = localBranchesWhereCommitShaIsHead.Select(r => r.CanonicalName);
+                    var csvNames = string.Join(", ", branchNames);
+                    const string moveBranchMsg = "Move one of the branches along a commit to remove warning";
+
+                    Logger.WriteWarning(string.Format("Found more than one local branch pointing at the commit '{0}' ({1}).", headSha, csvNames));
+                    var master = localBranchesWhereCommitShaIsHead.SingleOrDefault(n => n.Name == "master");
+                    if (master != null)
+                    {
+                        Logger.WriteWarning("Because one of the branches is 'master', will build master." + moveBranchMsg);
+                        master.Checkout();
+                    }
+                    else
+                    {
+                        var branchesWithoutSeparators = localBranchesWhereCommitShaIsHead.Where(b => !b.Name.Contains('/') && !b.Name.Contains('-')).ToList();
+                        if (branchesWithoutSeparators.Count == 1)
+                        {
+                            var branchWithoutSeparator = branchesWithoutSeparators[0];
+                            Logger.WriteWarning(string.Format("Choosing {0} as it is the only branch without / or - in it. " + moveBranchMsg, branchWithoutSeparator.CanonicalName));
+                            branchWithoutSeparator.Checkout();
+                        }
+                        else
+                        {
+                            throw new WarningException("Failed to try and guess branch to use. " + moveBranchMsg);
+                        }
+                    }
                 }
-
-                if (localBranchesWhereCommitShaIsHead.Count == 0)
+                else if (localBranchesWhereCommitShaIsHead.Count == 0)
                 {
                     Logger.WriteInfo(string.Format("No local branch pointing at the commit '{0}'. Fake branch needs to be created.", headSha));
                     CreateFakeBranchPointingAtThePullRequestTip(repo, authentication);