Introduce GlobalSettings.NativeLibraryPath

LibGit2Sharp.Tests/BlobFixture.cs

@@ -222,7 +222,7 @@ public void CanTellIfTheBlobContentLooksLikeBinary()
 
         private static void SkipIfNotSupported(string autocrlf)
         {
-            InconclusiveIf(() => autocrlf == "true" && IsRunningOnLinux(), "Non-Windows does not support core.autocrlf = true");
+            InconclusiveIf(() => autocrlf == "true" && IsRunningOnUnix(), "Non-Windows does not support core.autocrlf = true");
         }
     }
 }

LibGit2Sharp.Tests/GlobalSettingsFixture.cs

@@ -55,5 +55,14 @@ public void CanRetrieveValidVersionString()
                 Assert.True(matchGroups[i].Success);
             }
         }
+
+        [Fact]
+        public void TryingToResetNativeLibraryPathAfterLoadedThrows()
+        {
+            // Do something that loads the native library
+            Assert.NotNull(GlobalSettings.Version.Features);
+
+            Assert.Throws<LibGit2SharpException>(() => { GlobalSettings.NativeLibraryPath = "C:/Foo"; });
+        }
     }
 }

LibGit2Sharp.Tests/ShadowCopyFixture.cs

@@ -62,7 +62,7 @@ public void CanProbeForNativeBinariesFromAShadowCopiedAssembly()
             string cachedAssembliesPath = Path.Combine(setup.CachePath, setup.ApplicationName);
             Assert.True(cachedAssemblyLocation.StartsWith(cachedAssembliesPath));
 
-            if (!IsRunningOnLinux())
+            if (!IsRunningOnUnix())
             {
                 // ...that this cache doesn't contain the `NativeBinaries` folder
                 string cachedAssemblyParentPath = Path.GetDirectoryName(cachedAssemblyLocation);

LibGit2Sharp.Tests/TestHelpers/BaseFixture.cs

@@ -91,8 +91,8 @@ private static bool IsFileSystemCaseSensitiveInternal()
             return !isInsensitive;
         }
 
-        // Should match LibGit2Sharp.Core.NativeMethods.IsRunningOnLinux()
-        protected static bool IsRunningOnLinux()
+        // Should match LibGit2Sharp.Core.NativeMethods.IsRunningOnUnix()
+        protected static bool IsRunningOnUnix()
         {
             // see http://mono-project.com/FAQ%3a_Technical#Mono_Platforms
             var p = (int)Environment.OSVersion.Platform;

LibGit2Sharp/Core/NativeMethods.cs

@@ -64,44 +64,21 @@ internal static void RemoveHandle()
 
         static NativeMethods()
         {
-            if (!IsRunningOnLinux())
+            if (Platform.OperatingSystem == OperatingSystemType.Windows)
             {
-                string originalAssemblypath = new Uri(Assembly.GetExecutingAssembly().EscapedCodeBase).LocalPath;
+                string nativeLibraryPath = GlobalSettings.GetAndLockNativeLibraryPath();
 
-                string currentArchSubPath = "NativeBinaries/" + ProcessorArchitecture;
-
-                string path = Path.Combine(Path.GetDirectoryName(originalAssemblypath), currentArchSubPath);
+                string path = Path.Combine(nativeLibraryPath, Platform.ProcessorArchitecture);
 
                 const string pathEnvVariable = "PATH";
                 Environment.SetEnvironmentVariable(pathEnvVariable,
-                                                   String.Format(CultureInfo.InvariantCulture, "{0}{1}{2}", path, Path.PathSeparator, Environment.GetEnvironmentVariable(pathEnvVariable)));
+                    String.Format(CultureInfo.InvariantCulture, "{0}{1}{2}", path, Path.PathSeparator, Environment.GetEnvironmentVariable(pathEnvVariable)));
             }
 
             // See LibraryLifetimeObject description.
             lifetimeObject = new LibraryLifetimeObject();
         }
 
-        public static string ProcessorArchitecture
-        {
-            get
-            {
-                if (Environment.Is64BitProcess)
-                {
-                    return "amd64";
-                }
-
-                return "x86";
-            }
-        }
-
-        // Should match LibGit2Sharp.Tests.TestHelpers.BaseFixture.IsRunningOnLinux()
-        private static bool IsRunningOnLinux()
-        {
-            // see http://mono-project.com/FAQ%3a_Technical#Mono_Platforms
-            var p = (int)Environment.OSVersion.Platform;
-            return (p == 4) || (p == 6) || (p == 128);
-        }
-
         [DllImport(libgit2)]
         internal static extern GitErrorSafeHandle giterr_last();
 

LibGit2Sharp/Core/Platform.cs

@@ -0,0 +1,50 @@
+using System;
+using System.Collections.Generic;
+using System.Linq;
+using System.Text;
+
+namespace LibGit2Sharp.Core
+{
+    internal enum OperatingSystemType
+    {
+        Windows,
+        Unix,
+        MacOSX
+    }
+
+    internal class Platform
+    {
+        public static string ProcessorArchitecture
+        {
+            get
+            {
+                if (Environment.Is64BitProcess)
+                {
+                    return "amd64";
+                }
+
+                return "x86";
+            }
+        }
+
+        public static OperatingSystemType OperatingSystem
+        {
+            get
+            {
+                // See http://www.mono-project.com/docs/faq/technical/#how-to-detect-the-execution-platform
+                var platformId = (int)Environment.OSVersion.Platform;
+
+                switch ((int)Environment.OSVersion.Platform)
+                {
+                    case 4:
+                    case 128:
+                        return OperatingSystemType.Unix;
+                    case 6:
+                        return OperatingSystemType.MacOSX;
+                    default:
+                        return OperatingSystemType.Windows;
+                }
+            }
+        }
+    }
+}

LibGit2Sharp/GlobalSettings.cs

@@ -1,4 +1,6 @@
 using System;
+using System.IO;
+using System.Reflection;
 using LibGit2Sharp.Core;
 
 namespace LibGit2Sharp
@@ -12,6 +14,18 @@ public static class GlobalSettings
 
         private static LogConfiguration logConfiguration = LogConfiguration.None;
 
+        private static string nativeLibraryPath;
+        private static bool nativeLibraryPathLocked;
+
+        static GlobalSettings()
+        {
+            if (Platform.OperatingSystem == OperatingSystemType.Windows)
+            {
+                string managedPath = new Uri(Assembly.GetExecutingAssembly().EscapedCodeBase).LocalPath;
+                nativeLibraryPath = Path.Combine(Path.GetDirectoryName(managedPath), "NativeBinaries");
+            }
+        }
+
         /// <summary>
         /// Returns information related to the current LibGit2Sharp
         /// library.
@@ -108,5 +122,52 @@ public static LogConfiguration LogConfiguration
                 return logConfiguration;
             }
         }
+
+        /// <summary>
+        /// Sets a hint path for searching for native binaries: when
+        /// specified, native binaries will first be searched in a
+        /// subdirectory of the given path corresponding to the architecture
+        /// (eg, "x86" or "amd64") before falling back to the default
+        /// path ("NativeBinaries\x86" or "NativeBinaries\amd64" next
+        /// to the application).
+        /// <para>
+        /// This must be set before any other calls to the library,
+        /// and is not available on Unix platforms: see your dynamic
+        /// library loader's documentation for details.
+        /// </para>
+        /// </summary>
+        public static string NativeLibraryPath
+        {
+            get
+            {
+                if (Platform.OperatingSystem != OperatingSystemType.Windows)
+                {
+                    throw new LibGit2SharpException("Querying the native hint path is only supported on Windows platforms");
+                }
+
+                return nativeLibraryPath;
+            }
+
+            set
+            {
+                if (Platform.OperatingSystem != OperatingSystemType.Windows)
+                {
+                    throw new LibGit2SharpException("Setting the native hint path is only supported on Windows platforms");
+                }
+
+                if (nativeLibraryPathLocked)
+                {
+                    throw new LibGit2SharpException("You cannot set the native library path after it has been loaded");
+                }
+
+                nativeLibraryPath = value;
+            }
+        }
+
+        internal static string GetAndLockNativeLibraryPath()
+        {
+            nativeLibraryPathLocked = true;
+            return nativeLibraryPath;
+        }
     }
 }

LibGit2Sharp/LibGit2Sharp.csproj

@@ -68,6 +68,7 @@
     <Compile Include="CommitOptions.cs" />
     <Compile Include="CommitSortStrategies.cs" />
     <Compile Include="CompareOptions.cs" />
+    <Compile Include="Core\Platform.cs" />
     <Compile Include="DescribeOptions.cs" />
     <Compile Include="DescribeStrategy.cs" />
     <Compile Include="Core\GitDescribeFormatOptions.cs" />

LibGit2Sharp/Version.cs

@@ -98,7 +98,7 @@ private string RetrieveVersion()
                 InformationalVersion,
                 LibGit2SharpCommitSha,
                 LibGit2CommitSha,
-                NativeMethods.ProcessorArchitecture,
+                Platform.ProcessorArchitecture,
                 features);
         }