Fix octokit#1406 searching repos with underscore in name

Octokit.Tests.Integration/Clients/SearchClientTests.cs

@@ -71,6 +71,35 @@ public async Task SearchForFileNameInCodeWithoutTerm()
         Assert.NotEmpty(repos.Items);
     }
 
+    [IntegrationTest(Skip = "As this repository has been renamed, you cannot search for it's results.")]
+    public async Task SearchForFileNameInCodeWithoutTerm2()
+    {
+        var request = new SearchCodeRequest()
+        {
+            FileName = "project.json",
+            Repos = new RepositoryCollection { "adamcaudill/Psychson" }
+        };
+
+
+        var repos = await _gitHubClient.Search.SearchCode(request);
+
+        Assert.Empty(repos.Items);
+    }
+
+    [IntegrationTest]
+    public async Task SearchForFileNameInCodeWithoutTermWithUnderscore()
+    {
+        var request = new SearchCodeRequest()
+        {
+            FileName = "readme.md",
+            Repos = new RepositoryCollection { "Cultural-Rogue/_51Wp.XinFengSDK.Demo" }
+        };
+
+        var repos = await _gitHubClient.Search.SearchCode(request);
+
+        Assert.Empty(repos.Items);
+    }
+
     [IntegrationTest]
     public async Task SearchForWordInCode()
     {

Octokit/Helpers/StringExtensions.cs

@@ -122,7 +122,7 @@ static IEnumerable<string> SplitUpperCase(this string source)
         // the rule:
         // Username may only contain alphanumeric characters or single hyphens
         // and cannot begin or end with a hyphen
-        static readonly Regex nameWithOwner = new Regex("[a-z0-9.-]{1,}/[a-z0-9.-]{1,}",
+        static readonly Regex nameWithOwner = new Regex("[a-z0-9.-]{1,}/[a-z0-9.-_]{1,}",
 #if (!PORTABLE && !NETFX_CORE)
             RegexOptions.Compiled |
 #endif