fix(github): use one branch for status notification title and Branch field

CHANGELOG.md

@@ -33,6 +33,7 @@ Please ADD ALL Changes to the UNRELEASED SECTION and not a specific release
 - Added missing build;buildTransitive IncludeAssets on Serilog package reference required by FunFair.BuildCheck
 - CloudFormation task settings now live in Mappings so every deploy applies them, reducing ECS task memory from 4 GB to 1 GB
 - On a new stack, ECS tasks no longer fail to start with a 'log group does not exist' error, and their final logs are kept when the stack is deleted, because the ECS application log group is now created before the tasks and removed after them (#421)
+- Status notifications now pick one branch consistently for the embed title and Branch field (prefer release/*, then main, else first) - #434
 ### Changed
 - Dependencies - Updated NSubstitute.Analyzers.CSharp to 1.0.17
 - Switched to use minimal APIs

src/BuildBot.GitHub.Tests/Publishers/GithubStatusNotificationHandlerTests.cs

@@ -1,4 +1,4 @@
-using System;
+using System;
 using System.Threading;
 using System.Threading.Tasks;
 using BuildBot.Discord.Models;
@@ -166,4 +166,33 @@ await handler.Handle(
         Assert.Equal(expected: "Build finished for ci/build from BuildBot ((unknown))", actual: embed.Title);
         Assert.Equal(expected: new DiscordEmbedField(Name: "Branch", Value: "(unknown)"), actual: embed.Fields[1]);
     }
+
+    [Theory]
+    [InlineData("feature/one,main,release/1.2.3", "release/1.2.3")]
+    [InlineData("main,Release/2.0", "Release/2.0")]
+    [InlineData("feature/one,main,develop", "main")]
+    [InlineData("main,feature/one", "main")]
+    [InlineData("feature/one,feature/two", "feature/one")]
+    [InlineData("develop", "develop")]
+    public async Task PublishedEmbedUsesSameSelectedBranchInTitleAndFieldAsync(
+        string branchNames,
+        string expectedBranch
+    )
+    {
+        (IMediator mediator, GithubStatusNotificationHandler handler) = this.CreateHandler();
+
+        Branch[] branches = Array.ConvertAll(
+            array: branchNames.Split(','),
+            converter: static name => new Branch(name: name)
+        );
+
+        await handler.Handle(
+            notification: new(MakeStatusWithBranches(state: "success", branches: branches)),
+            cancellationToken: this.CancellationToken()
+        );
+
+        DiscordEmbed embed = mediator.PublishedEmbed();
+        Assert.Equal(expected: $"Build finished for ci/build from BuildBot ({expectedBranch})", actual: embed.Title);
+        Assert.Equal(expected: new DiscordEmbedField(Name: "Branch", Value: expectedBranch), actual: embed.Fields[1]);
+    }
 }

src/BuildBot.GitHub/Publishers/GithubStatusNotificationHandler.cs

@@ -52,26 +52,40 @@ private static bool IsPendingBuild(in Status message)
 
     private static DiscordEmbed BuildStatusMessage(in Status message)
     {
-        Branch? lastBranch = message.Branches.Count > 0 ? message.Branches[^1] : null;
-        string branchName = lastBranch?.Name ?? "(unknown)";
+        string branchName = GetBranchName(message.Branches);
 
         return new(
             Title: $"{message.Description} for {message.Context} from {message.Repository.Name} ({branchName})",
             Url: EmbedUrl.FromString(message.TargetUrl),
             Description: $"Built at {message.StatusCommit.Sha}",
             Color: GetEmbedColor(message),
-            Fields: GetFields(message)
+            Fields: [AddHeadCommitEmbed(message.StatusCommit), AddBranchEmbed(branchName)]
         );
     }
 
-    private static IReadOnlyList<DiscordEmbedField> GetFields(in Status message)
+    private static string GetBranchName(IReadOnlyList<Branch> branches)
     {
-        return [AddHeadCommitEmbed(message.StatusCommit), AddBranchEmbed(message)];
+        IReadOnlyList<string> names = [.. branches.Select(static b => b.Name)];
+
+        return names.FirstOrDefault(IsReleaseBranch)
+            ?? names.FirstOrDefault(IsMainBranch)
+            ?? names.FirstOrDefault()
+            ?? "(unknown)";
+    }
+
+    private static bool IsReleaseBranch(string name)
+    {
+        return name.StartsWith(value: "release/", comparisonType: StringComparison.OrdinalIgnoreCase);
+    }
+
+    private static bool IsMainBranch(string name)
+    {
+        return StringComparer.Ordinal.Equals(x: name, y: "main");
     }
 
-    private static DiscordEmbedField AddBranchEmbed(in Status message)
+    private static DiscordEmbedField AddBranchEmbed(string branchName)
     {
-        return new(Name: "Branch", Value: message.Branches.Select(static b => b.Name).FirstOrDefault() ?? "(unknown)");
+        return new(Name: "Branch", Value: branchName);
     }
 
     private static DiscordEmbedField AddHeadCommitEmbed(in StatusCommit statusCommit)