Add support for resolving tags

Author: jcansdale

src/GitHub.App/Services/GitHubContextService.cs

@@ -281,21 +281,22 @@ public bool TryOpenFile(string repositoryDir, GitHubContext context)
 
                 foreach (var (commitish, path) in objectish)
                 {
-                    var remoteRef = $"refs/remotes/{remoteName}/{commitish}";
-                    var commit = repository.Lookup(remoteRef);
-                    if (commit == null)
+                    var resolveRefs = new[] { $"refs/remotes/{remoteName}/{commitish}", $"refs/tags/{commitish}" };
+                    foreach (var resolveRef in resolveRefs)
                     {
-                        continue;
+                        var commit = repository.Lookup(resolveRef);
+                        if (commit != null)
+                        {
+                            var blob = repository.Lookup($"{resolveRef}:{path}");
+                            if (blob != null)
+                            {
+                                return (resolveRef, path, commit.Sha);
+                            }
+
+                            // Resolved commitish but not path
+                            return (resolveRef, null, commit.Sha);
+                        }
                     }
-
-                    var blob = repository.Lookup($"{remoteRef}:{path}");
-                    if (blob == null)
-                    {
-                        // Resolved commitish but not path
-                        return (remoteRef, null, commit.Sha);
-                    }
-
-                    return (remoteRef, path, commit.Sha);
                 }
 
                 return (null, null, null);

test/GitHub.App.UnitTests/Services/GitHubContextServiceTests.cs

@@ -335,6 +335,7 @@ public class TheResolveBlobMethod
         [TestCase("https://github.com/github/VisualStudio/blob/master/foo.cs", "refs/remotes/origin/master", null, "refs/remotes/origin/master", null, CommitSha, Description = "Resolve commit only")]
         [TestCase("https://github.com/github/VisualStudio/blob/36d6b0bb6e319337180d523281c42d9611744e66/src/code.cs", CommitSha, CommitSha + ":src/code.cs", CommitSha, "src/code.cs", CommitSha, Description = "Resolve commit only")]
         [TestCase("https://github.com/github/VisualStudio/commit/8cf9a268c497adb4fc0a14572253165e179dd11e", "8cf9a268c497adb4fc0a14572253165e179dd11e", null, null, null, null)]
+        [TestCase("https://github.com/github/VisualStudio/blob/v2.5.3.2888/build.cmd", "refs/tags/v2.5.3.2888", "refs/tags/v2.5.3.2888:build.cmd", "refs/tags/v2.5.3.2888", "build.cmd", CommitSha)]
         public void ResolveBlob(string url, string commitish, string objectish, string expectCommitish, string expectPath, string expectCommitSha)
         {
             var repositoryDir = "repositoryDir";