(#495) Allow milestones without issues

This commit introduces a new configuration value in the
GitReleaseManager.yaml file, which is disabled by default.  When
enabled, it will be used to control whether the creation of an "empty"
release is allowed.  This will make use of a new "empty" Scriban
template, which will be introduced in the next commit.

Author: Jericho

src/GitReleaseManager.Core/Configuration/Config.cs

@@ -27,6 +27,7 @@ public Config()
                 ShaSectionHeading = "SHA256 Hashes of the release artifacts",
                 ShaSectionLineFormat = "- `{1}\t{0}`",
                 AllowUpdateToPublishedRelease = false,
+                AllowMilestonesWithoutIssues = false,
                 IncludeContributors = false,
             };
 

src/GitReleaseManager.Core/Configuration/CreateConfig.cs

@@ -35,6 +35,9 @@ public class CreateConfig
         [YamlMember(Alias = "allow-update-to-published")]
         public bool AllowUpdateToPublishedRelease { get; set; }
 
+        [YamlMember(Alias = "allow-milestone-without-issues")]
+        public bool AllowMilestonesWithoutIssues { get; set; }
+
         [YamlMember(Alias = "include-contributors")]
         public bool IncludeContributors { get; set; }
     }

src/GitReleaseManager.Core/ReleaseNotes/ReleaseNotesBuilder.cs

@@ -58,7 +58,7 @@ public async Task<string> BuildReleaseNotesAsync(string user, string repository,
 
             var numberOfCommits = await _vcsProvider.GetCommitsCountAsync(_user, _repository, @base, head).ConfigureAwait(false);
 
-            if (issues.Count == 0)
+            if (issues.Count == 0 && !_configuration.Create.AllowMilestonesWithoutIssues)
             {
                 var logMessage = string.Format(CultureInfo.CurrentCulture, "No closed issues have been found for milestone {0}, or all assigned issues are meant to be excluded from release notes, aborting release creation.", _milestoneTitle);
                 throw new InvalidOperationException(logMessage);