Parse diffs to get real line numbers for comments.

The `PullRequestReviewComment.Position` field refers to a line number in the diff between the PR `Head` and `Base`. Generate and parse this diff to get the line number in the file at which the comment should be placed.
2017-04-07 15:12:52 +02:00 · 2017-04-07 15:12:52 +02:00 · bb6aa7ef28
--- a/.ncrunch/GitHub.InlineReviews.v3.ncrunchproject
+++ b/.ncrunch/GitHub.InlineReviews.v3.ncrunchproject
@ -1,5 +1,6 @@
 <ProjectConfiguration>
  <Settings>
+    <PreventSigningOfAssembly>True</PreventSigningOfAssembly>
    <PreviouslyBuiltSuccessfully>True</PreviouslyBuiltSuccessfully>
  </Settings>
 </ProjectConfiguration>
--- a/src/GitHub.App/Models/PullRequestReviewCommentModel.cs
+++ b/src/GitHub.App/Models/PullRequestReviewCommentModel.cs
@ -6,8 +6,11 @@ namespace GitHub.Models
    [NullGuard(ValidationFlags.None)]
    public class PullRequestReviewCommentModel : IPullRequestReviewCommentModel
    {
+        public int Id { get; set; }
        public string Path { get; set; }
        public int? Position { get; set; }
+        public string CommitId { get; set; }
+        public string DiffHunk { get; set; }
        public IAccount User { get; set; }
        public string Body { get; set; }
        public DateTimeOffset UpdatedAt { get; set; }
--- a/src/GitHub.App/Services/GitClient.cs
+++ b/src/GitHub.App/Services/GitClient.cs
@ -159,6 +159,35 @@ namespace GitHub.Services
            });
        }

+        public Task<Patch> Compare(
+            IRepository repository,
+            string sha1,
+            string sha2,
+            string path)
+        {
+            Guard.ArgumentNotNull(repository, nameof(repository));
+            Guard.ArgumentNotEmptyString(sha1, nameof(sha1));
+            Guard.ArgumentNotEmptyString(sha2, nameof(sha2));
+
+            return Task.Factory.StartNew(() =>
+            {
+                var commit1 = repository.Lookup<Commit>(sha1);
+                var commit2 = repository.Lookup<Commit>(sha2);
+
+                if (commit1 != null && commit2 != null)
+                {
+                    return repository.Diff.Compare<Patch>(
+                        commit1.Tree,
+                        commit2.Tree,
+                        new[] { path });
+                }
+                else
+                {
+                    return null;
+                }
+            });
+        }
+
        public Task<T> GetConfig<T>(IRepository repository, string key)
        {
            Guard.ArgumentNotNull(repository, nameof(repository));
--- a/src/GitHub.App/Services/ModelService.cs
+++ b/src/GitHub.App/Services/ModelService.cs
@ -407,8 +407,11 @@ namespace GitHub.Services
                Comments = prCacheItem.Comments.Select(x =>
                    (IPullRequestReviewCommentModel)new PullRequestReviewCommentModel
                    {
+                        Id = x.Id,
                        Path = x.Path,
                        Position = x.Position,
+                        CommitId = x.CommitId,
+                        DiffHunk = x.DiffHunk,
                        User = Create(x.User),
                        Body = x.Body,
                        UpdatedAt = x.UpdatedAt,
@ -623,15 +626,21 @@ namespace GitHub.Services

            public PullRequestReviewCommentCacheItem(PullRequestReviewComment comment)
            {
+                Id = comment.Id;
                Path = comment.Path;
                Position = comment.Position;
+                CommitId = comment.CommitId;
+                DiffHunk = comment.DiffHunk;
                User = new AccountCacheItem(comment.User);
                Body = comment.Body;
                UpdatedAt = comment.UpdatedAt;
            }

+            public int Id { get; }
            public string Path { get; set; }
            public int? Position { get; set; }
+            public string CommitId { get; set; }
+            public string DiffHunk { get; set; }
            public AccountCacheItem User { get; set; }
            public string Body { get; set; }
            public DateTimeOffset UpdatedAt { get; set; }
--- a/src/GitHub.App/Services/PullRequestReviewSession.cs
+++ b/src/GitHub.App/Services/PullRequestReviewSession.cs
@ -12,37 +12,23 @@ namespace GitHub.Services
        Dictionary<string, List<IPullRequestReviewCommentModel>> comments;

        public PullRequestReviewSession(
-            ILocalRepositoryModel repository,
-            IEnumerable<IPullRequestReviewCommentModel> comments)
+            IPullRequestModel pullRequest,
+            ILocalRepositoryModel repository)
        {
+            PullRequest = pullRequest;
            Repository = repository;
-            this.comments = comments.GroupBy(x => x.Path)
+            this.comments = pullRequest.Comments.GroupBy(x => x.Path)
                .ToDictionary(x => x.Key, x => x.ToList());
        }

+        public IPullRequestModel PullRequest { get; }
        public ILocalRepositoryModel Repository { get; }

-        public IEnumerable<IPullRequestReviewCommentModel> GetCommentsForFile(string filePath)
+        public IReadOnlyList<IPullRequestReviewCommentModel> GetCommentsForFile(string path)
        {
-            var relativePath = RootedPathToRelativePath(filePath).Replace('\\', '/');
-            var result = Empty;
-            comments.TryGetValue(relativePath, out result);
-            return result ?? Empty;
-        }
-
-        string RootedPathToRelativePath(string path)
-        {
-            if (Path.IsPathRooted(path))
-            {
-                var repoRoot = Repository.LocalPath;
-
-                if (path.StartsWith(repoRoot) && path.Length > repoRoot.Length + 1)
-                {
-                    return path.Substring(repoRoot.Length + 1);
-                }
-            }
-
-            return null;
+            List<IPullRequestReviewCommentModel> result;
+            path = path.Replace('\\', '/');
+            return comments.TryGetValue(path, out result) ? result : Empty;
        }
    }
 }
--- a/src/GitHub.App/ViewModels/PullRequestDetailViewModel.cs
+++ b/src/GitHub.App/ViewModels/PullRequestDetailViewModel.cs
@ -486,7 +486,7 @@ namespace GitHub.ViewModels
        {
            if (IsCheckedOut)
            {
-                var session = new PullRequestReviewSession(repository, Model.Comments);
+                var session = new PullRequestReviewSession(Model, repository);
                sessionManager.NotifySessionChanged(session);
            }
            else
--- a/src/GitHub.Exports.Reactive/Services/IGitClient.cs
+++ b/src/GitHub.Exports.Reactive/Services/IGitClient.cs
@ -68,6 +68,18 @@ namespace GitHub.Services
        /// </returns>
        Task<TreeChanges> Compare(IRepository repository, string sha1, string sha2, bool detectRenames = false);

+        /// <summary>
+        /// Compares a file in two commits.
+        /// </summary>
+        /// <param name="repository">The repository</param>
+        /// <param name="sha1">The SHA of the first commit.</param>
+        /// <param name="sha2">The SHA of the second commit.</param>
+        /// <param name="path">The relative path to the file.</param>
+        /// <returns>
+        /// A <see cref="Patch"/> object or null if one of the commits or the file could not be found in the repository.
+        /// </returns>
+        Task<Patch> Compare(IRepository repository, string sha1, string sha2, string path);
+
        /// Gets the value of a configuration key.
        /// </summary>
        /// <param name="repository">The repository.</param>
--- a/src/GitHub.Exports/Models/IPullRequestReviewCommentModel.cs
+++ b/src/GitHub.Exports/Models/IPullRequestReviewCommentModel.cs
@ -4,8 +4,11 @@ namespace GitHub.Models
 {
    public interface IPullRequestReviewCommentModel
    {
+        int Id { get; }
        string Path { get; }
        int? Position { get; }
+        string CommitId { get; }
+        string DiffHunk { get; }
        IAccount User { get; }
        string Body { get; }
        DateTimeOffset UpdatedAt { get; }
--- a/src/GitHub.Exports/Services/IPullRequestReviewSession.cs
+++ b/src/GitHub.Exports/Services/IPullRequestReviewSession.cs
@ -6,6 +6,9 @@ namespace GitHub.Services
 {
    public interface IPullRequestReviewSession
    {
-        IEnumerable<IPullRequestReviewCommentModel> GetCommentsForFile(string filePath);
+        IPullRequestModel PullRequest { get; }
+        ILocalRepositoryModel Repository { get; }
+
+        IReadOnlyList<IPullRequestReviewCommentModel> GetCommentsForFile(string path);
    }
 }
--- a/src/GitHub.InlineReviews/GitHub.InlineReviews.csproj
+++ b/src/GitHub.InlineReviews/GitHub.InlineReviews.csproj
@ -1,5 +1,6 @@
 <?xml version="1.0" encoding="utf-8"?>
 <Project ToolsVersion="14.0" DefaultTargets="Build" xmlns="http://schemas.microsoft.com/developer/msbuild/2003">
+  <Import Project="..\..\packages\LibGit2Sharp.NativeBinaries.1.0.129\build\LibGit2Sharp.NativeBinaries.props" Condition="Exists('..\..\packages\LibGit2Sharp.NativeBinaries.1.0.129\build\LibGit2Sharp.NativeBinaries.props')" />
  <Import Project="..\..\packages\Microsoft.VSSDK.BuildTools.14.3.25407\build\Microsoft.VSSDK.BuildTools.props" Condition="Exists('..\..\packages\Microsoft.VSSDK.BuildTools.14.3.25407\build\Microsoft.VSSDK.BuildTools.props')" />
  <PropertyGroup>
    <MinimumVisualStudioVersion>14.0</MinimumVisualStudioVersion>
@ -53,7 +54,11 @@
    <WarningLevel>4</WarningLevel>
  </PropertyGroup>
  <ItemGroup>
+    <Compile Include="..\common\SolutionInfo.cs">
+      <Link>Properties\SolutionInfo.cs</Link>
+    </Compile>
    <Compile Include="InlineReviewsPackage.cs" />
+    <Compile Include="Models\InlineCommentModel.cs" />
    <Compile Include="Peek\ReviewPeekableItem.cs" />
    <Compile Include="Peek\ReviewPeekableItemSource.cs" />
    <Compile Include="Peek\ReviewPeekableItemSourceProvider.cs" />
@ -65,6 +70,8 @@
    <Compile Include="Peek\ReviewPeekSessionCreationOptions.cs" />
    <Compile Include="Properties\AssemblyInfo.cs" />
    <Compile Include="SampleData\PullRequestReviewCommentDesigner.cs" />
+    <Compile Include="Services\IInlineCommentBuilder.cs" />
+    <Compile Include="Services\InlineCommentBuilder.cs" />
    <Compile Include="Tags\ReviewGlyph.xaml.cs">
      <DependentUpon>ReviewGlyph.xaml</DependentUpon>
    </Compile>
@ -104,6 +111,10 @@
      <Project>{9aea02db-02b5-409c-b0ca-115d05331a6b}</Project>
      <Name>GitHub.Exports</Name>
    </ProjectReference>
+    <ProjectReference Include="..\GitHub.Extensions\GitHub.Extensions.csproj">
+      <Project>{6AFE2E2D-6DB0-4430-A2EA-F5F5388D2F78}</Project>
+      <Name>GitHub.Extensions</Name>
+    </ProjectReference>
    <ProjectReference Include="..\GitHub.UI\GitHub.UI.csproj">
      <Project>{346384dd-2445-4a28-af22-b45f3957bd89}</Project>
      <Name>GitHub.UI</Name>
@ -126,6 +137,10 @@
    <Reference Include="EnvDTE90, Version=9.0.0.0, Culture=neutral, PublicKeyToken=b03f5f7f11d50a3a">
      <EmbedInteropTypes>False</EmbedInteropTypes>
    </Reference>
+    <Reference Include="LibGit2Sharp, Version=0.22.0.0, Culture=neutral, PublicKeyToken=7cbde695407f0333, processorArchitecture=MSIL">
+      <HintPath>..\..\packages\LibGit2Sharp.0.22.0\lib\net40\LibGit2Sharp.dll</HintPath>
+      <Private>True</Private>
+    </Reference>
    <Reference Include="Microsoft.Build.Framework" />
    <Reference Include="Microsoft.CSharp" />
    <Reference Include="Microsoft.VisualStudio.CommandBars, Version=8.0.0.0, Culture=neutral, PublicKeyToken=b03f5f7f11d50a3a">
@ -279,14 +294,16 @@
      <SubType>Designer</SubType>
    </Page>
  </ItemGroup>
+  <ItemGroup />
  <Import Project="$(MSBuildToolsPath)\Microsoft.CSharp.targets" />
-  <Import Project="$(VSToolsPath)\VSSDK\Microsoft.VsSDK.targets" Condition="'$(VSToolsPath)' != ''" />
+  <Import Project="$(VSToolsPath)\VSSDK\Microsoft.VsSDK.targets" Condition="'$(VSToolsPath)' != '' And '$(NCrunch)' != '1'" />
  <Target Name="EnsureNuGetPackageBuildImports" BeforeTargets="PrepareForBuild">
    <PropertyGroup>
      <ErrorText>This project references NuGet package(s) that are missing on this computer. Use NuGet Package Restore to download them.  For more information, see http://go.microsoft.com/fwlink/?LinkID=322105. The missing file is {0}.</ErrorText>
    </PropertyGroup>
    <Error Condition="!Exists('..\..\packages\Microsoft.VSSDK.BuildTools.14.3.25407\build\Microsoft.VSSDK.BuildTools.props')" Text="$([System.String]::Format('$(ErrorText)', '..\..\packages\Microsoft.VSSDK.BuildTools.14.3.25407\build\Microsoft.VSSDK.BuildTools.props'))" />
    <Error Condition="!Exists('..\..\packages\Microsoft.VSSDK.BuildTools.14.3.25407\build\Microsoft.VSSDK.BuildTools.targets')" Text="$([System.String]::Format('$(ErrorText)', '..\..\packages\Microsoft.VSSDK.BuildTools.14.3.25407\build\Microsoft.VSSDK.BuildTools.targets'))" />
+    <Error Condition="!Exists('..\..\packages\LibGit2Sharp.NativeBinaries.1.0.129\build\LibGit2Sharp.NativeBinaries.props')" Text="$([System.String]::Format('$(ErrorText)', '..\..\packages\LibGit2Sharp.NativeBinaries.1.0.129\build\LibGit2Sharp.NativeBinaries.props'))" />
  </Target>
  <Import Project="..\..\packages\Microsoft.VSSDK.BuildTools.14.3.25407\build\Microsoft.VSSDK.BuildTools.targets" Condition="Exists('..\..\packages\Microsoft.VSSDK.BuildTools.14.3.25407\build\Microsoft.VSSDK.BuildTools.targets')" />
  <!-- To modify your build process, add your task inside one of the targets below and uncomment it. 
--- a/src/GitHub.InlineReviews/Models/InlineCommentModel.cs
+++ b/src/GitHub.InlineReviews/Models/InlineCommentModel.cs
@ -0,0 +1,25 @@
+using System;
+using GitHub.Models;
+
+namespace GitHub.InlineReviews.Models
+{
+    public class InlineCommentModel
+    {
+        public InlineCommentModel(int lineNumber, IPullRequestReviewCommentModel original)
+        {
+            LineNumber = lineNumber;
+            Original = original;
+        }
+
+        public int LineNumber { get; private set; }
+        public IPullRequestReviewCommentModel Original { get; }
+
+        public void UpdatePosition(int editLine, int editDelta)
+        {
+            if (LineNumber >= editLine)
+            {
+                LineNumber += editDelta;
+            }
+        }
+    }
+}
--- a/src/GitHub.InlineReviews/Properties/AssemblyInfo.cs
+++ b/src/GitHub.InlineReviews/Properties/AssemblyInfo.cs
@ -1,33 +1,6 @@
 using System.Reflection;
-using System.Runtime.CompilerServices;
 using System.Runtime.InteropServices;

-// General Information about an assembly is controlled through the following 
-// set of attributes. Change these attribute values to modify the information
-// associated with an assembly.
 [assembly: AssemblyTitle("GitHub.InlineReviews")]
-[assembly: AssemblyDescription("")]
-[assembly: AssemblyConfiguration("")]
-[assembly: AssemblyCompany("")]
-[assembly: AssemblyProduct("GitHub.InlineReviews")]
-[assembly: AssemblyCopyright("")]
-[assembly: AssemblyTrademark("")]
-[assembly: AssemblyCulture("")]
-
-// Setting ComVisible to false makes the types in this assembly not visible 
-// to COM components.  If you need to access a type in this assembly from 
-// COM, set the ComVisible attribute to true on that type.
-[assembly: ComVisible(false)]
-
-// Version information for an assembly consists of the following four values:
-//
-//      Major Version
-//      Minor Version 
-//      Build Number
-//      Revision
-//
-// You can specify all the values or you can default the Build and Revision Numbers 
-// by using the '*' as shown below:
-// [assembly: AssemblyVersion("1.0.*")]
-[assembly: AssemblyVersion("1.0.0.0")]
-[assembly: AssemblyFileVersion("1.0.0.0")]
+[assembly: AssemblyDescription("Provides inline viewing of PR review comments")]
+[assembly: Guid("3bf91177-3d16-425d-9c62-50a86cf26298")]
--- a/src/GitHub.InlineReviews/SampleData/PullRequestReviewCommentDesigner.cs
+++ b/src/GitHub.InlineReviews/SampleData/PullRequestReviewCommentDesigner.cs
@ -6,8 +6,11 @@ namespace GitHub.InlineReviews.SampleData
 {
    public class PullRequestReviewCommentDesigner : IPullRequestReviewCommentModel
    {
+        public int Id => 1;
        public string Path => string.Empty;
        public int? Position => 1;
+        public string CommitId => null;
+        public string DiffHunk => null;
        public DateTimeOffset UpdatedAt => DateTime.Now.Subtract(TimeSpan.FromDays(3));
        public IAccount User => new AccountDesigner { Login = "shana", IsUser = true };
        public string Body => @"You can use a `CompositeDisposable` type here, it's designed to handle disposables in an optimal way (you can just call `Dispose()` on it and it will handle disposing everything it holds).";
--- a/src/GitHub.InlineReviews/Services/IInlineCommentBuilder.cs
+++ b/src/GitHub.InlineReviews/Services/IInlineCommentBuilder.cs
@ -0,0 +1,14 @@
+using System.Collections.Generic;
+using System.Threading.Tasks;
+using GitHub.InlineReviews.Models;
+using GitHub.Services;
+
+namespace GitHub.InlineReviews.Services
+{
+    public interface IInlineCommentBuilder
+    {
+        Task<IList<InlineCommentModel>> Build(
+            string path,
+            IPullRequestReviewSession session);
+    }
+}
--- a/src/GitHub.InlineReviews/Services/InlineCommentBuilder.cs
+++ b/src/GitHub.InlineReviews/Services/InlineCommentBuilder.cs
@ -0,0 +1,125 @@
+using System;
+using System.Collections.Generic;
+using System.ComponentModel.Composition;
+using System.IO;
+using System.Linq;
+using System.Threading.Tasks;
+using GitHub.Extensions;
+using GitHub.InlineReviews.Models;
+using GitHub.Services;
+using LibGit2Sharp;
+
+namespace GitHub.InlineReviews.Services
+{
+    [Export(typeof(IInlineCommentBuilder))]
+    [PartCreationPolicy(CreationPolicy.Shared)]
+    public class InlineCommentBuilder : IInlineCommentBuilder
+    {
+        readonly IGitClient gitClient;
+
+        [ImportingConstructor]
+        public InlineCommentBuilder(IGitClient gitClient)
+        {
+            Guard.ArgumentNotNull(gitClient, nameof(gitClient));
+
+            this.gitClient = gitClient;
+        }
+
+        public async Task<IList<InlineCommentModel>> Build(
+            string path,
+            IPullRequestReviewSession session)
+        {
+            Guard.ArgumentNotNull(path, nameof(path));
+            Guard.ArgumentNotNull(session, nameof(session));
+
+            var result = new List<InlineCommentModel>();
+            var repo = GitService.GitServiceHelper.GetRepository(session.Repository.LocalPath);
+            var changes = await gitClient.Compare(
+                repo,
+                session.PullRequest.Head.Sha,
+                session.PullRequest.Base.Sha,
+                path);
+            var comments = session.GetCommentsForFile(path);
+            var diffPositions = comments
+                .Where(x => x.Position.HasValue)
+                .Select(x => x.Position.Value)
+                .OrderBy(x => x)
+                .Distinct();
+            var lineMap = MapDiffPositions(changes.Content, diffPositions);
+
+            foreach (var comment in comments)
+            {
+                int lineNumber;
+
+                if (comment.Position.HasValue && lineMap.TryGetValue(comment.Position.Value, out lineNumber))
+                {
+                    result.Add(new InlineCommentModel(lineNumber, comment));
+                }
+            }
+
+            return result;
+        }
+
+        /// <summary>
+        /// Maps lines in a diff to lines in the source file.
+        /// </summary>
+        /// <param name="diff">The diff.</param>
+        /// <param name="positions">The diff lines to map.</param>
+        /// <returns>
+        /// A dictionary mapping 1-based diff line numbers to 0-based file line numbers.
+        /// </returns>
+        public IDictionary<int, int> MapDiffPositions(string diff, IEnumerable<int> positions)
+        {
+            Guard.ArgumentNotNull(diff, nameof(diff));
+            Guard.ArgumentNotNull(positions, nameof(positions));
+
+            var diffLine = -1;
+            var sourceLine = -1;
+            var positionEnumerator = positions.GetEnumerator();
+            var result = new Dictionary<int, int>();
+
+            positionEnumerator.MoveNext();
+
+            using (var reader = new StringReader(diff))
+            {
+                string line;
+
+                while ((line = reader.ReadLine()) != null)
+                {
+                    if (line.StartsWith("@@"))
+                    {
+                        if (sourceLine == -1) diffLine = 0;
+                        sourceLine = ReadLineFromHunkHeader(line) - 1;
+                    }
+
+                    if (positionEnumerator.Current == diffLine)
+                    {
+                        result.Add(diffLine, sourceLine);
+                        if (!positionEnumerator.MoveNext()) break;
+                    }
+
+                    if (diffLine >= 0)
+                    {
+                        ++diffLine;
+                        if (!line.StartsWith('-')) ++sourceLine;
+                    }
+                }
+            }
+
+            return result;
+        }
+
+        int ReadLineFromHunkHeader(string line)
+        {
+            int plus = line.IndexOf('+');
+            int comma = line.IndexOf(',', plus);
+            return int.Parse(line.Substring(plus + 1, comma - (plus + 1)));
+        }
+
+        public class ChunkRange
+        {
+            public int DiffLine { get; set; }
+            public int SourceLine { get; set; }
+        }
+    }
+}
--- a/src/GitHub.InlineReviews/Tags/ReviewTagger.cs
+++ b/src/GitHub.InlineReviews/Tags/ReviewTagger.cs
@ -5,6 +5,11 @@ using Microsoft.VisualStudio.Text;
 using Microsoft.VisualStudio.Text.Tagging;
 using GitHub.Services;
 using GitHub.Models;
+using System.IO;
+using LibGit2Sharp;
+using GitHub.InlineReviews.Models;
+using GitHub.InlineReviews.Services;
+using System.Threading.Tasks;

 namespace GitHub.InlineReviews.Tags
 {
@ -12,13 +17,19 @@ namespace GitHub.InlineReviews.Tags
    {
        readonly ITextBuffer buffer;
        readonly IPullRequestReviewSessionManager sessionManager;
+        readonly IInlineCommentBuilder builder;
        readonly IDisposable subscription;
-        List<InlineComment> comments;
+        string path;
+        IList<InlineCommentModel> comments;

-        public ReviewTagger(ITextBuffer buffer, IPullRequestReviewSessionManager sessionManager)
+        public ReviewTagger(
+            ITextBuffer buffer,
+            IPullRequestReviewSessionManager sessionManager,
+            IInlineCommentBuilder builder)
        {
            this.buffer = buffer;
            this.sessionManager = sessionManager;
+            this.builder = builder;
            this.buffer.Changed += Buffer_Changed;
            subscription = sessionManager.SessionChanged.Subscribe(SessionChanged);
        }
@ -40,9 +51,9 @@ namespace GitHub.InlineReviews.Tags
                    var endLine = span.End.GetContainingLine().LineNumber;

                    var spanComments = comments.Where(x =>
-                        x.Position >= startLine &&
-                        x.Position <= endLine)
-                        .GroupBy(x => x.Position);
+                        x.LineNumber >= startLine &&
+                        x.LineNumber <= endLine)
+                        .GroupBy(x => x.LineNumber);

                    foreach (var entry in spanComments)
                    {
@ -55,35 +66,37 @@ namespace GitHub.InlineReviews.Tags
            }
        }

-        void SessionChanged(IPullRequestReviewSession session)
+        static string RootedPathToRelativePath(string path, string basePath)
        {
-            if (session != null)
+            if (Path.IsPathRooted(path))
            {
-                var document = buffer.Properties.GetProperty<ITextDocument>(typeof(ITextDocument));
-                comments = CreateInlineComments(session.GetCommentsForFile(document.FilePath));
-
-                var entireFile = new SnapshotSpan(buffer.CurrentSnapshot, 0, buffer.CurrentSnapshot.Length);
-                TagsChanged?.Invoke(this, new SnapshotSpanEventArgs(entireFile));
-            }
-            else
-            {
-                comments = null;
-            }
-        }
-
-        List<InlineComment> CreateInlineComments(IEnumerable<IPullRequestReviewCommentModel> comments)
-        {
-            var result = new List<InlineComment>();
-
-            foreach (var comment in comments)
-            {
-                if (comment.Position.HasValue)
+                if (path.StartsWith(basePath) && path.Length > basePath.Length + 1)
                {
-                    result.Add(new InlineComment(comment));
+                    return path.Substring(basePath.Length + 1);
                }
            }

-            return result;
+            return null;
+        }
+
+        void NotifyTagsChanged()
+        {
+            var entireFile = new SnapshotSpan(buffer.CurrentSnapshot, 0, buffer.CurrentSnapshot.Length);
+            TagsChanged?.Invoke(this, new SnapshotSpanEventArgs(entireFile));
+        }
+
+        async void SessionChanged(IPullRequestReviewSession session)
+        {
+            comments = null;
+            NotifyTagsChanged();
+
+            if (session != null)
+            {
+                var document = buffer.Properties.GetProperty<ITextDocument>(typeof(ITextDocument));
+                path = RootedPathToRelativePath(document.FilePath, session.Repository.LocalPath);
+                comments = await builder.Build(path, session);
+                NotifyTagsChanged();
+            }
        }

        void Buffer_Changed(object sender, TextContentChangedEventArgs e)
@ -101,25 +114,5 @@ namespace GitHub.InlineReviews.Tags
                }
            }
        }
-
-        class InlineComment
-        {
-            public InlineComment(IPullRequestReviewCommentModel original)
-            {
-                Position = original.Position.Value - 1;
-                Original = original;
-            }
-
-            public int Position { get; private set; }
-            public IPullRequestReviewCommentModel Original { get; }
-
-            public void UpdatePosition(int editLine, int editDelta)
-            {
-                if (Position >= editLine)
-                {
-                    Position += editDelta;
-                }
-            }
-        }
    }
 }
--- a/src/GitHub.InlineReviews/Tags/ReviewTaggerProvider.cs
+++ b/src/GitHub.InlineReviews/Tags/ReviewTaggerProvider.cs
@ -1,5 +1,6 @@
 using System;
 using System.ComponentModel.Composition;
+using GitHub.InlineReviews.Services;
 using GitHub.Services;
 using Microsoft.VisualStudio.Text;
 using Microsoft.VisualStudio.Text.Tagging;
@ -13,16 +14,20 @@ namespace GitHub.InlineReviews.Tags
    class ReviewTaggerProvider : ITaggerProvider
    {
        readonly IPullRequestReviewSessionManager sessionManager;
+        readonly IInlineCommentBuilder builder;

        [ImportingConstructor]
-        public ReviewTaggerProvider(IPullRequestReviewSessionManager sessionManager)
+        public ReviewTaggerProvider(
+            IPullRequestReviewSessionManager sessionManager,
+            IInlineCommentBuilder builder)
        {
            this.sessionManager = sessionManager;
+            this.builder = builder;
        }

        public ITagger<T> CreateTagger<T>(ITextBuffer buffer) where T : ITag
        {
-            return new ReviewTagger(buffer, sessionManager) as ITagger<T>;
+            return new ReviewTagger(buffer, sessionManager, builder) as ITagger<T>;
        }
    }
 }
--- a/src/GitHub.InlineReviews/packages.config
+++ b/src/GitHub.InlineReviews/packages.config
@ -1,5 +1,7 @@
 <?xml version="1.0" encoding="utf-8"?>
 <packages>
+  <package id="LibGit2Sharp" version="0.22.0" targetFramework="net461" />
+  <package id="LibGit2Sharp.NativeBinaries" version="1.0.129" targetFramework="net461" />
  <package id="Microsoft.VisualStudio.CoreUtility" version="14.3.25407" targetFramework="net461" />
  <package id="Microsoft.VisualStudio.Imaging" version="14.3.25407" targetFramework="net452" />
  <package id="Microsoft.VisualStudio.Language.Intellisense" version="14.3.25407" targetFramework="net461" />
--- a/src/UnitTests/GitHub.InlineReviews/InlineCommentBuilderTests.cs
+++ b/src/UnitTests/GitHub.InlineReviews/InlineCommentBuilderTests.cs
@ -0,0 +1,22 @@
+using System;
+using GitHub.InlineReviews.Services;
+using GitHub.Services;
+using NSubstitute;
+using UnitTests.Properties;
+using Xunit;
+
+namespace UnitTests.GitHub.InlineReviews
+{
+    public class InlineCommentBuilderTests
+    {
+        [Fact]
+        public void CorrectlyMapsCommentPositions()
+        {
+            var target = new InlineCommentBuilder(Substitute.For<IGitClient>());
+            var diff = Resources.pr_573_apiclient_diff;
+            var result = target.MapDiffPositions(diff, new[] { 31 });
+
+            Assert.Equal(87, result[31]);
+        }
+    }
+}
--- a/src/UnitTests/Properties/Resources.Designer.cs
+++ b/src/UnitTests/Properties/Resources.Designer.cs
@ -0,0 +1,89 @@
+//------------------------------------------------------------------------------
+// <auto-generated>
+//     This code was generated by a tool.
+//     Runtime Version:4.0.30319.42000
+//
+//     Changes to this file may cause incorrect behavior and will be lost if
+//     the code is regenerated.
+// </auto-generated>
+//------------------------------------------------------------------------------
+
+namespace UnitTests.Properties {
+    using System;
+    
+    
+    /// <summary>
+    ///   A strongly-typed resource class, for looking up localized strings, etc.
+    /// </summary>
+    // This class was auto-generated by the StronglyTypedResourceBuilder
+    // class via a tool like ResGen or Visual Studio.
+    // To add or remove a member, edit your .ResX file then rerun ResGen
+    // with the /str option, or rebuild your VS project.
+    [global::System.CodeDom.Compiler.GeneratedCodeAttribute("System.Resources.Tools.StronglyTypedResourceBuilder", "4.0.0.0")]
+    [global::System.Diagnostics.DebuggerNonUserCodeAttribute()]
+    [global::System.Runtime.CompilerServices.CompilerGeneratedAttribute()]
+    internal class Resources {
+        
+        private static global::System.Resources.ResourceManager resourceMan;
+        
+        private static global::System.Globalization.CultureInfo resourceCulture;
+        
+        [global::System.Diagnostics.CodeAnalysis.SuppressMessageAttribute("Microsoft.Performance", "CA1811:AvoidUncalledPrivateCode")]
+        internal Resources() {
+        }
+        
+        /// <summary>
+        ///   Returns the cached ResourceManager instance used by this class.
+        /// </summary>
+        [global::System.ComponentModel.EditorBrowsableAttribute(global::System.ComponentModel.EditorBrowsableState.Advanced)]
+        internal static global::System.Resources.ResourceManager ResourceManager {
+            get {
+                if (object.ReferenceEquals(resourceMan, null)) {
+                    global::System.Resources.ResourceManager temp = new global::System.Resources.ResourceManager("UnitTests.Properties.Resources", typeof(Resources).Assembly);
+                    resourceMan = temp;
+                }
+                return resourceMan;
+            }
+        }
+        
+        /// <summary>
+        ///   Overrides the current thread's CurrentUICulture property for all
+        ///   resource lookups using this strongly typed resource class.
+        /// </summary>
+        [global::System.ComponentModel.EditorBrowsableAttribute(global::System.ComponentModel.EditorBrowsableState.Advanced)]
+        internal static global::System.Globalization.CultureInfo Culture {
+            get {
+                return resourceCulture;
+            }
+            set {
+                resourceCulture = value;
+            }
+        }
+        
+        /// <summary>
+        ///   Looks up a localized string similar to diff --git a/src/GitHub.App/Api/ApiClient.cs b/src/GitHub.App/Api/ApiClient.cs
+        ///index 6745236..79adcf3 100644
+        ///--- a/src/GitHub.App/Api/ApiClient.cs
+        ///+++ b/src/GitHub.App/Api/ApiClient.cs
+        ///@@ -8,6 +8,7 @@
+        /// using System.Security.Cryptography;
+        /// using System.Text;
+        /// using GitHub.Primitives;
+        ///+using NLog;
+        /// using NullGuard;
+        /// using Octokit;
+        /// using Octokit.Reactive;
+        ///@@ -18,8 +19,6 @@
+        /// using System.Collections.Generic;
+        /// using GitHub.Models;
+        /// using GitHub.Extensions;
+        ///-using GitHub.Infrastructure;
+        ///-using S [rest of string was truncated]&quot;;.
+        /// </summary>
+        internal static string pr_573_apiclient_diff {
+            get {
+                return ResourceManager.GetString("pr_573_apiclient_diff", resourceCulture);
+            }
+        }
+    }
+}
--- a/src/UnitTests/Properties/Resources.resx
+++ b/src/UnitTests/Properties/Resources.resx
@ -0,0 +1,124 @@
+<?xml version="1.0" encoding="utf-8"?>
+<root>
+  <!-- 
+    Microsoft ResX Schema 
+    
+    Version 2.0
+    
+    The primary goals of this format is to allow a simple XML format 
+    that is mostly human readable. The generation and parsing of the 
+    various data types are done through the TypeConverter classes 
+    associated with the data types.
+    
+    Example:
+    
+    ... ado.net/XML headers & schema ...
+    <resheader name="resmimetype">text/microsoft-resx</resheader>
+    <resheader name="version">2.0</resheader>
+    <resheader name="reader">System.Resources.ResXResourceReader, System.Windows.Forms, ...</resheader>
+    <resheader name="writer">System.Resources.ResXResourceWriter, System.Windows.Forms, ...</resheader>
+    <data name="Name1"><value>this is my long string</value><comment>this is a comment</comment></data>
+    <data name="Color1" type="System.Drawing.Color, System.Drawing">Blue</data>
+    <data name="Bitmap1" mimetype="application/x-microsoft.net.object.binary.base64">
+        <value>[base64 mime encoded serialized .NET Framework object]</value>
+    </data>
+    <data name="Icon1" type="System.Drawing.Icon, System.Drawing" mimetype="application/x-microsoft.net.object.bytearray.base64">
+        <value>[base64 mime encoded string representing a byte array form of the .NET Framework object]</value>
+        <comment>This is a comment</comment>
+    </data>
+                
+    There are any number of "resheader" rows that contain simple 
+    name/value pairs.
+    
+    Each data row contains a name, and value. The row also contains a 
+    type or mimetype. Type corresponds to a .NET class that support 
+    text/value conversion through the TypeConverter architecture. 
+    Classes that don't support this are serialized and stored with the 
+    mimetype set.
+    
+    The mimetype is used for serialized objects, and tells the 
+    ResXResourceReader how to depersist the object. This is currently not 
+    extensible. For a given mimetype the value must be set accordingly:
+    
+    Note - application/x-microsoft.net.object.binary.base64 is the format 
+    that the ResXResourceWriter will generate, however the reader can 
+    read any of the formats listed below.
+    
+    mimetype: application/x-microsoft.net.object.binary.base64
+    value   : The object must be serialized with 
+            : System.Runtime.Serialization.Formatters.Binary.BinaryFormatter
+            : and then encoded with base64 encoding.
+    
+    mimetype: application/x-microsoft.net.object.soap.base64
+    value   : The object must be serialized with 
+            : System.Runtime.Serialization.Formatters.Soap.SoapFormatter
+            : and then encoded with base64 encoding.
+
+    mimetype: application/x-microsoft.net.object.bytearray.base64
+    value   : The object must be serialized into a byte array 
+            : using a System.ComponentModel.TypeConverter
+            : and then encoded with base64 encoding.
+    -->
+  <xsd:schema id="root" xmlns="" xmlns:xsd="http://www.w3.org/2001/XMLSchema" xmlns:msdata="urn:schemas-microsoft-com:xml-msdata">
+    <xsd:import namespace="http://www.w3.org/XML/1998/namespace" />
+    <xsd:element name="root" msdata:IsDataSet="true">
+      <xsd:complexType>
+        <xsd:choice maxOccurs="unbounded">
+          <xsd:element name="metadata">
+            <xsd:complexType>
+              <xsd:sequence>
+                <xsd:element name="value" type="xsd:string" minOccurs="0" />
+              </xsd:sequence>
+              <xsd:attribute name="name" use="required" type="xsd:string" />
+              <xsd:attribute name="type" type="xsd:string" />
+              <xsd:attribute name="mimetype" type="xsd:string" />
+              <xsd:attribute ref="xml:space" />
+            </xsd:complexType>
+          </xsd:element>
+          <xsd:element name="assembly">
+            <xsd:complexType>
+              <xsd:attribute name="alias" type="xsd:string" />
+              <xsd:attribute name="name" type="xsd:string" />
+            </xsd:complexType>
+          </xsd:element>
+          <xsd:element name="data">
+            <xsd:complexType>
+              <xsd:sequence>
+                <xsd:element name="value" type="xsd:string" minOccurs="0" msdata:Ordinal="1" />
+                <xsd:element name="comment" type="xsd:string" minOccurs="0" msdata:Ordinal="2" />
+              </xsd:sequence>
+              <xsd:attribute name="name" type="xsd:string" use="required" msdata:Ordinal="1" />
+              <xsd:attribute name="type" type="xsd:string" msdata:Ordinal="3" />
+              <xsd:attribute name="mimetype" type="xsd:string" msdata:Ordinal="4" />
+              <xsd:attribute ref="xml:space" />
+            </xsd:complexType>
+          </xsd:element>
+          <xsd:element name="resheader">
+            <xsd:complexType>
+              <xsd:sequence>
+                <xsd:element name="value" type="xsd:string" minOccurs="0" msdata:Ordinal="1" />
+              </xsd:sequence>
+              <xsd:attribute name="name" type="xsd:string" use="required" />
+            </xsd:complexType>
+          </xsd:element>
+        </xsd:choice>
+      </xsd:complexType>
+    </xsd:element>
+  </xsd:schema>
+  <resheader name="resmimetype">
+    <value>text/microsoft-resx</value>
+  </resheader>
+  <resheader name="version">
+    <value>2.0</value>
+  </resheader>
+  <resheader name="reader">
+    <value>System.Resources.ResXResourceReader, System.Windows.Forms, Version=4.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089</value>
+  </resheader>
+  <resheader name="writer">
+    <value>System.Resources.ResXResourceWriter, System.Windows.Forms, Version=4.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089</value>
+  </resheader>
+  <assembly alias="System.Windows.Forms" name="System.Windows.Forms, Version=4.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089" />
+  <data name="pr_573_apiclient_diff" type="System.Resources.ResXFileRef, System.Windows.Forms">
+    <value>..\Resources\pr-573-apiclient-diff.txt;System.String, mscorlib, Version=4.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089;Windows-1252</value>
+  </data>
+</root>
--- a/src/UnitTests/Resources/pr-573-apiclient-diff.txt
+++ b/src/UnitTests/Resources/pr-573-apiclient-diff.txt
@ -0,0 +1,74 @@
+diff --git a/src/GitHub.App/Api/ApiClient.cs b/src/GitHub.App/Api/ApiClient.cs
+index 6745236..79adcf3 100644
+--- a/src/GitHub.App/Api/ApiClient.cs
+++ b/src/GitHub.App/Api/ApiClient.cs
+@@ -8,6 +8,7 @@
+ using System.Security.Cryptography;
+ using System.Text;
+ using GitHub.Primitives;
+using NLog;
+ using NullGuard;
+ using Octokit;
+ using Octokit.Reactive;
+@@ -18,8 +19,6 @@
+ using System.Collections.Generic;
+ using GitHub.Models;
+ using GitHub.Extensions;
+-using GitHub.Infrastructure;
+-using Serilog;
+ 
+ namespace GitHub.Api
+ {
+@@ -27,7 +26,7 @@ public partial class ApiClient : IApiClient
+     {
+         const string ScopesHeader = "X-OAuth-Scopes";
+         const string ProductName = Info.ApplicationInfo.ApplicationDescription;
+-        static readonly ILogger log = LogManager.ForContext<ApiClient>();
+        static readonly Logger log = LogManager.GetCurrentClassLogger();
+         static readonly Uri userEndpoint = new Uri("user", UriKind.Relative);
+ 
+         readonly IObservableGitHubClient gitHubClient;
+@@ -85,7 +84,7 @@ public IObservable<UserAndScopes> GetUser()
+             }
+             else
+             {
+-                log.Error("Error reading scopes: /user succeeded but {ScopesHeader} was not present.", ScopesHeader);
+                log.Error($"Error reading scopes: /user succeeded but {ScopesHeader} was not present.");
+             }
+ 
+             return new UserAndScopes(response.Body, scopes);
+@@ -176,7 +175,7 @@ static string GetSha256Hash(string input)
+             }
+             catch (Exception e)
+             {
+-                log.Error(e, "IMPOSSIBLE! Generating Sha256 hash caused an exception.");
+                log.Error("IMPOSSIBLE! Generating Sha256 hash caused an exception.", e);
+                 return null;
+             }
+         }
+@@ -194,14 +193,14 @@ static string GetMachineNameSafe()
+             }
+             catch (Exception e)
+             {
+-                log.Information(e, "Failed to retrieve host name using `DNS.GetHostName`.");
+                log.Info("Failed to retrieve host name using `DNS.GetHostName`.", e);
+                 try
+                 {
+                     return Environment.MachineName;
+                 }
+                 catch (Exception ex)
+                 {
+-                    log.Information(ex, "Failed to retrieve host name using `Environment.MachineName`.");
+                    log.Info("Failed to retrieve host name using `Environment.MachineName`.", ex);
+                     return "(unknown)";
+                 }
+             }
+@@ -222,7 +221,7 @@ static string GetMachineIdentifier()
+             }
+             catch (Exception e)
+             {
+-                log.Information(e, "Could not retrieve MAC address. Fallback to using machine name.");
+                log.Info("Could not retrieve MAC address. Fallback to using machine name.", e);
+                 return GetMachineNameSafe();
+             }
+         }
--- a/src/UnitTests/UnitTests.csproj
+++ b/src/UnitTests/UnitTests.csproj
@ -246,6 +246,7 @@
    <Compile Include="GitHub.Exports\LocalRepositoryModelTests.cs" />
    <Compile Include="GitHub.Extensions\GuardTests.cs" />
    <Compile Include="GitHub.Extensions\UriExtensionTests.cs" />
+    <Compile Include="GitHub.InlineReviews\InlineCommentBuilderTests.cs" />
    <Compile Include="GitHub.Primitives\UriStringTests.cs" />
    <Compile Include="GitHub.UI\Converters.cs" />
    <Compile Include="GitHub.UI\TestAutomation\ResourceValueTests.cs" />
@ -260,6 +261,11 @@
    <Compile Include="Helpers\TestBaseClass.cs" />
    <Compile Include="Helpers\TestLoginCache.cs" />
    <Compile Include="Helpers\TestSharedCache.cs" />
+    <Compile Include="Properties\Resources.Designer.cs">
+      <AutoGen>True</AutoGen>
+      <DesignTime>True</DesignTime>
+      <DependentUpon>Resources.resx</DependentUpon>
+    </Compile>
    <Compile Include="Substitutes.cs" />
    <Compile Include="TestDoubles\FakeCommitLog.cs" />
    <Compile Include="TestDoubles\FakeMenuCommandService.cs" />
@ -333,6 +339,10 @@
      <Project>{6afe2e2d-6db0-4430-a2ea-f5f5388d2f78}</Project>
      <Name>GitHub.Extensions</Name>
    </ProjectReference>
+    <ProjectReference Include="..\GitHub.InlineReviews\GitHub.InlineReviews.csproj">
+      <Project>{7f5ed78b-74a3-4406-a299-70cfb5885b8b}</Project>
+      <Name>GitHub.InlineReviews</Name>
+    </ProjectReference>
    <ProjectReference Include="..\GitHub.TeamFoundation.14\GitHub.TeamFoundation.14.csproj">
      <Project>{161DBF01-1DBF-4B00-8551-C5C00F26720D}</Project>
      <Name>GitHub.TeamFoundation.14</Name>
@ -363,6 +373,13 @@
  </ItemGroup>
  <ItemGroup>
    <Content Include="FodyWeavers.xml" />
+    <None Include="Resources\pr-573-apiclient-diff.txt" />
+  </ItemGroup>
+  <ItemGroup>
+    <EmbeddedResource Include="Properties\Resources.resx">
+      <Generator>ResXFileCodeGenerator</Generator>
+      <LastGenOutput>Resources.Designer.cs</LastGenOutput>
+    </EmbeddedResource>
  </ItemGroup>
  <Import Project="$(MSBuildToolsPath)\Microsoft.CSharp.targets" />
  <Target Name="EnsureNuGetPackageBuildImports" BeforeTargets="PrepareForBuild">