Abort prepare-release command when version on current branch is not incremented

src/NerdBank.GitVersioning.Tests/ReleaseManagerTests.cs

@@ -392,12 +392,30 @@ public void PrepareRelease_MasterWithVersionDecrement(string initialVersion, str
         this.WriteVersionFile(versionOptions);
 
         // running PrepareRelease should result in an error
-        // because we're trying to add a prerelease tag to a version without prerelease tag
+        // because we're setting the version on master to a lower version
         this.AssertError(
             () => new ReleaseManager().PrepareRelease(this.RepoPath, releaseUnstableTag, (nextVersion == null ? null : Version.Parse(nextVersion))),
             ReleasePreparationError.VersionDecrement);
     }
 
+    [Theory]
+    [InlineData("1.2", "1.2")]
+    public void PrepareRelease_MasterWithoutVersionIncrement(string initialVersion, string nextVersion)
+    {
+        // create and configure repository
+        this.InitializeSourceControl();
+
+        // create version.json
+        var versionOptions = new VersionOptions() { Version = SemanticVersion.Parse(initialVersion) };
+        this.WriteVersionFile(versionOptions);
+
+        // running PrepareRelease should result in an error
+        // because we're trying to set master to the version it already has
+        this.AssertError(
+            () => new ReleaseManager().PrepareRelease(this.RepoPath, null, (nextVersion == null ? null : Version.Parse(nextVersion))),
+            ReleasePreparationError.NoVersionIncrement);
+    }
+
     [Fact]
     public void PrepareRelease_DetachedHead()
     {

src/NerdBank.GitVersioning/ReleaseManager.cs

@@ -47,6 +47,11 @@ public enum ReleasePreparationError
             /// </summary>
             VersionDecrement,
 
+            /// <summary>
+            /// Branch cannot be set to the specified version because the new version is not higher than the current version
+            /// </summary>
+            NoVersionIncrement,
+
             /// <summary>
             /// Cannot create a branch because it already exists
             /// </summary>
@@ -273,6 +278,14 @@ public void PrepareRelease(string projectDirectory, string releaseUnstableTag =
 
             var nextDevVersion = this.GetNextDevVersion(versionOptions, nextVersion, versionIncrement);
 
+            // check if the current version on the main branch is different from the next version
+            // otherwise, both the release branch and the dev branch would have the same version
+            if (versionOptions.Version.Version == nextDevVersion.Version)
+            {
+                this.stderr.WriteLine($"Version on '{originalBranchName}' is already set to next version {nextDevVersion.Version}.");
+                throw new ReleasePreparationException(ReleasePreparationError.NoVersionIncrement);
+            }
+
             // check if the release branch already exists
             if (repository.Branches[releaseBranchName] != null)
             {

src/nbgv/Program.cs

@@ -736,6 +736,7 @@ private static int OnPrepareReleaseCommand(string project, string nextVersion, s
                     case ReleaseManager.ReleasePreparationError.NoVersionFile:
                         return (int)ExitCodes.NoVersionJsonFound;
                     case ReleaseManager.ReleasePreparationError.VersionDecrement:
+                    case ReleaseManager.ReleasePreparationError.NoVersionIncrement:
                         return (int)ExitCodes.InvalidVersionSpec;
                     case ReleaseManager.ReleasePreparationError.BranchAlreadyExists:
                         return (int)ExitCodes.BranchAlreadyExists;