GitVersion not incrementing as expected on mainline mode

Describe the bug We are not getting build versions as desired when using mainline mode.

Our GitVersion.yml is simply

mode: Mainline

Expected Behavior

Some background: We have a master branch and a preview branch to represent release rings. We do features and fixes in features/* and fix/* branches and then merge to preview…and then finally to master.

We have CI that builds and publishes a nuget package and we use the syntax *-preview* to lock in consumers to our preview ring.

Example:

• master is currently at 0.1.2
• preview (currently identical to master) is at 0.1.2-preview0088
• We create a new feature off of preview in a branch feature/something and it gets the version 0.1.3-feature-something0001
• We merge feature/something into preview and preview gets the version 0.1.3-preview0001
• We merge preview into master and master gets the version 0.1.3
• Repeat the process

Actual Behavior

This seems to work sometimes, but not others, and when it doesn’t work, it is very difficult to get things re-aligned.

• preview (currently identical to master) is at 0.1.2-preview0088
• We create a new feature off of preview in a branch feature/somethingnew and it gets the version 0.1.2-feature-somethingnew0001

[asbjornu]

You can read about the different modes in the documentation.

[HHobeck]

Please tak a look to the following integration test which I have been executed on current main branch:

[Test]
public void JustATestFor2888()
{
    var configuration = GitFlowConfigurationBuilder.New
        .WithVersioningMode(VersioningMode.Mainline)
        .WithBranch("develop", _ => _
            .WithRegularExpression("^preview$")
            .WithVersioningMode(VersioningMode.ContinuousDeployment)
            .WithIncrement(IncrementStrategy.Patch)
            .WithLabel("preview")
        )
        .WithBranch("feature", _ => _
            .WithVersioningMode(VersioningMode.ContinuousDeployment)
            .WithIncrement(IncrementStrategy.Patch)
            .WithLabel("{BranchName}")
        )
        .Build();

    using var fixture = new EmptyRepositoryFixture("main");

    fixture.MakeATaggedCommit("0.1.2");

    fixture.BranchTo("preview");
    fixture.BranchTo("feature/something");
    fixture.MakeACommit();

    // ✅ succeeds as expected
    fixture.AssertFullSemver("0.1.3-something.1", configuration);

    fixture.MakeACommit();

    // ✅ succeeds as expected
    fixture.AssertFullSemver("0.1.3-something.2", configuration);

    fixture.Checkout("preview");
    fixture.MergeNoFF("feature/something");
    fixture.Remove("feature/something");

    // ✅ succeeds as expected
    fixture.AssertFullSemver("0.1.3-preview.3", configuration);

    fixture.Checkout("main");
    fixture.MergeNoFF("preview");

    // ✅ succeeds as expected
    fixture.AssertFullSemver("0.1.3", configuration);

    fixture.ApplyTag("0.1.3");

    // ✅ succeeds as expected
    fixture.AssertFullSemver("0.1.3", configuration);
}