Added validation when creating reference

Octokit.Tests/Models/NewReferenceTests.cs

@@ -0,0 +1,25 @@
+using System;
+
+using Octokit;
+
+using Xunit;
+
+public class NewReferenceTests
+{
+    public class TheCtor
+    {
+        [Fact]
+        public void EnforcesRefsPrefix()
+        {
+            var create = new NewReference("heads/develop", "sha");
+
+            Assert.Equal(create.Ref, "refs/heads/develop");
+        }
+
+        [Fact]
+        public void ThrowsExceptionIfRefHasLessThanTwoSlashes()
+        {
+            Assert.Throws<FormatException>(() => new NewReference("refs/develop", "sha"));
+        }
+    }
+}

Octokit.Tests/Octokit.Tests.csproj

@@ -111,6 +111,7 @@
     <Compile Include="Http\ResponseTests.cs" />
     <Compile Include="Http\RequestTests.cs" />
     <Compile Include="Models\CommitTests.cs" />
+    <Compile Include="Models\NewReferenceTests.cs" />
     <Compile Include="Models\MilestoneRequestTests.cs" />
     <Compile Include="Models\IssueRequestTests.cs" />
     <Compile Include="Models\ModelExtensionsTests.cs" />

Octokit/Models/Request/NewReference.cs

@@ -1,17 +1,40 @@
-namespace Octokit
+using System;
+using System.Linq;
+
+namespace Octokit
 {
     public class NewReference
     {
-        public NewReference(string @ref, string sha)
+        const string _refsPrefix = "refs";
+
+        public NewReference(string reference, string sha)
         {
-            Ensure.ArgumentNotNullOrEmptyString(@ref, "ref");
+            Ensure.ArgumentNotNullOrEmptyString(reference, "ref");
             Ensure.ArgumentNotNullOrEmptyString(sha, "sha");
 
-            Ref = @ref;
+            Ref = GetReference(reference);
             Sha = sha;
         }
 
         public string Ref { get; private set; }
         public string Sha { get; private set; }
+
+        static string GetReference(string reference)
+        {
+            var parts = reference.Split('/').ToList();
+
+            var refsPart = parts.FirstOrDefault();
+            if (refsPart != null && refsPart != _refsPrefix)
+            {
+                parts.Insert(0, _refsPrefix);
+            }
+
+            if (parts.Count < 3)
+            {
+                throw new FormatException("Reference must start with 'refs' and have at least two slashes.");
+            }
+
+            return string.Join("/", parts);
+        }
     }
 }