Add support for showing conflicting files in repo update error

src/Tgstation.Server.Host/Components/Events/EventType.cs

@@ -85,7 +85,7 @@
 		InstanceAutoUpdateStart,
 
 		/// <summary>
-		/// Parameters: Base sha, target sha, base reference, target reference
+		/// Parameters: Base sha, target sha, base reference, target reference, all conflicting files
 		/// </summary>
 		[EventScript("RepoMergeConflict")]
 		RepoMergeConflict,

src/Tgstation.Server.Host/Components/Repository/IRepository.cs

@@ -69,8 +69,8 @@ namespace Tgstation.Server.Host.Components.Repository
 		/// <param name="updateSubmodules">If a submodule update should be attempted after the merge.</param>
 		/// <param name="progressReporter">The <see cref="JobProgressReporter"/> to report progress of the operation.</param>
 		/// <param name="cancellationToken">The <see cref="CancellationToken"/> for the operation.</param>
-		/// <returns>A <see cref="Task{TResult}"/> resulting in a <see cref="Nullable{T}"/> <see cref="bool"/> representing the merge result that is <see langword="true"/> after a fast forward or up to date, <see langword="false"/> on a non-fast-forward, <see langword="null"/> on a conflict.</returns>
-		Task<bool?> AddTestMerge(
+		/// <returns>A <see cref="Task{TResult}"/> resulting in the <see cref="TestMergeResult"/>.</returns>
+		Task<TestMergeResult> AddTestMerge(
 			TestMergeParameters testMergeParameters,
 			string committerName,
 			string committerEmail,

src/Tgstation.Server.Host/Components/Repository/Repository.cs

@@ -172,7 +172,7 @@ namespace Tgstation.Server.Host.Components.Repository
 
 		/// <inheritdoc />
 #pragma warning disable CA1506 // TODO: Decomplexify
-		public async Task<bool?> AddTestMerge(
+		public async Task<TestMergeResult> AddTestMerge(
 			TestMergeParameters testMergeParameters,
 			string committerName,
 			string committerEmail,
@@ -225,6 +225,7 @@ namespace Tgstation.Server.Host.Components.Repository
 			var progressFactor = 1.0 / (updateSubmodules ? 3 : 2);
 
 			var sig = new Signature(new Identity(committerName, committerEmail), DateTimeOffset.UtcNow);
+			List<string> conflictedPaths = null;
 			await Task.Factory.StartNew(
 				() =>
 				{
@@ -279,7 +280,7 @@ namespace Tgstation.Server.Host.Components.Repository
 						result = libGitRepo.Merge(testMergeParameters.TargetCommitSha, sig, new MergeOptions
 						{
 							CommitOnSuccess = commitMessage == null,
-							FailOnConflict = true,
+							FailOnConflict = false, // Needed to get conflicting files
 							FastForwardStrategy = FastForwardStrategy.NoFastForward,
 							SkipReuc = true,
 							OnCheckoutProgress = CheckoutProgressHandler(
@@ -295,6 +296,12 @@ namespace Tgstation.Server.Host.Components.Repository
 
 					if (result.Status == MergeStatus.Conflicts)
 					{
+						var repoStatus = libGitRepo.RetrieveStatus();
+						conflictedPaths = new List<string>();
+						foreach (var file in repoStatus)
+							if (file.State == FileStatus.Conflicted)
+								conflictedPaths.Add(file.FilePath);
+
 						var revertTo = originalCommit.CanonicalName ?? originalCommit.Tip.Sha;
 						logger.LogDebug("Merge conflict, aborting and reverting to {0}", revertTo);
 						progressReporter.ReportProgress(0);
@@ -306,23 +313,29 @@ namespace Tgstation.Server.Host.Components.Repository
 				},
 				cancellationToken,
 				DefaultIOManager.BlockingTaskCreationOptions,
-				TaskScheduler.Current)
-				;
+				TaskScheduler.Current);
 
 			if (result.Status == MergeStatus.Conflicts)
 			{
+				var arguments = new List<string>
+				{
+					originalCommit.Tip.Sha,
+					testMergeParameters.TargetCommitSha,
+					originalCommit.FriendlyName ?? UnknownReference,
+					testMergeBranchName,
+				};
+
+				arguments.AddRange(conflictedPaths);
+
 				await eventConsumer.HandleEvent(
 					EventType.RepoMergeConflict,
-					new List<string>
-					{
-						originalCommit.Tip.Sha,
-						testMergeParameters.TargetCommitSha,
-						originalCommit.FriendlyName ?? UnknownReference,
-						testMergeBranchName,
-					},
-					cancellationToken)
-					;
-				return null;
+					arguments,
+					cancellationToken);
+				return new TestMergeResult
+				{
+					Status = result.Status,
+					ConflictingFiles = conflictedPaths,
+				};
 			}
 
 			if (result.Status != MergeStatus.UpToDate)
@@ -356,10 +369,12 @@ namespace Tgstation.Server.Host.Components.Repository
 					testMergeParameters.TargetCommitSha,
 					testMergeParameters.Comment,
 				},
-				cancellationToken)
-				;
+				cancellationToken);
 
-			return result.Status != MergeStatus.NonFastForward;
+			return new TestMergeResult
+			{
+				Status = result.Status,
+			};
 		}
 #pragma warning restore CA1506
 

src/Tgstation.Server.Host/Components/Repository/RepositoryUpdateService.cs

@@ -4,6 +4,8 @@ using System.Linq;
 using System.Threading;
 using System.Threading.Tasks;
 
+using LibGit2Sharp;
+
 using Microsoft.AspNetCore.Mvc;
 using Microsoft.EntityFrameworkCore;
 using Microsoft.Extensions.Logging;
@@ -499,11 +501,11 @@ namespace Tgstation.Server.Host.Components.Repository
 								NextProgressReporter($"Test merge #{newTestMerge.Number}"),
 								cancellationToken);
 
-							if (mergeResult == null)
+							if (mergeResult.Status == MergeStatus.Conflicts)
 								throw new JobException(
 									ErrorCode.RepoTestMergeConflict,
 									new JobException(
-										$"Test Merge #{newTestMerge.Number} at {newTestMerge.TargetCommitSha[..7]} conflicted!"));
+										$"Test Merge #{newTestMerge.Number} at {newTestMerge.TargetCommitSha[..7]} conflicted! Conflicting files:{Environment.NewLine}{String.Join(Environment.NewLine, mergeResult.ConflictingFiles.Select(file => $"\t- /{file}"))}"));
 
 							Models.TestMerge fullTestMerge;
 							try

src/Tgstation.Server.Host/Components/Repository/TestMergeResult.cs

@@ -0,0 +1,22 @@
+using System.Collections.Generic;
+
+using LibGit2Sharp;
+
+namespace Tgstation.Server.Host.Components.Repository
+{
+	/// <summary>
+	/// Represents the result of a repository test merge attempt.
+	/// </summary>
+	public sealed class TestMergeResult
+	{
+		/// <summary>
+		/// The resulting <see cref="MergeStatus"/>.
+		/// </summary>
+		public MergeStatus Status { get; init; }
+
+		/// <summary>
+		/// List of conflicting file paths relative to the repository root. Only present if <see cref="Status"/> is <see cref="MergeStatus.Conflicts"/>.
+		/// </summary>
+		public IReadOnlyList<string> ConflictingFiles { get; init; }
+	}
+}