tests: allow override of resources directory

We attempt to determine the test resource directory based on the path of
the currently running assembly.  If this fails, or if the user is running
in a nonstandard environment (perhaps not building out of source) then
provide users a mechanism to explicitly specify the path to the resources.

Author: ethomson

LibGit2Sharp.Tests/TestHelpers/BaseFixture.cs

@@ -59,25 +59,32 @@ private static void SetUpTestEnvironment()
         {
             IsFileSystemCaseSensitive = IsFileSystemCaseSensitiveInternal();
 
-            string initialAssemblyParentFolder = Directory.GetParent(new Uri(typeof(BaseFixture).GetTypeInfo().Assembly.CodeBase).LocalPath).FullName;
+            var resourcesPath = Environment.GetEnvironmentVariable("LIBGIT2SHARP_RESOURCES");
 
-            const string sourceRelativePath = @"../../../../LibGit2Sharp.Tests/Resources";
-            ResourcesDirectory = new DirectoryInfo(Path.Combine(initialAssemblyParentFolder, sourceRelativePath));
+            if (resourcesPath == null)
+            {
+                string initialAssemblyParentFolder = Directory.GetParent(new Uri(typeof(BaseFixture).GetTypeInfo().Assembly.CodeBase).LocalPath).FullName;
+                const string sourceRelativePath = @"../../../../LibGit2Sharp.Tests/Resources";
+
+                resourcesPath = Path.Combine(initialAssemblyParentFolder, sourceRelativePath);
+            }
+
+            ResourcesDirectory = new DirectoryInfo(resourcesPath);
 
             // Setup standard paths to our test repositories
-            BareTestRepoPath = Path.Combine(sourceRelativePath, "testrepo.git");
-            StandardTestRepoWorkingDirPath = Path.Combine(sourceRelativePath, "testrepo_wd");
+            BareTestRepoPath = Path.Combine(ResourcesDirectory.FullName, "testrepo.git");
+            StandardTestRepoWorkingDirPath = Path.Combine(ResourcesDirectory.FullName, "testrepo_wd");
             StandardTestRepoPath = Path.Combine(StandardTestRepoWorkingDirPath, "dot_git");
-            ShallowTestRepoPath = Path.Combine(sourceRelativePath, "shallow.git");
-            MergedTestRepoWorkingDirPath = Path.Combine(sourceRelativePath, "mergedrepo_wd");
-            MergeRenamesTestRepoWorkingDirPath = Path.Combine(sourceRelativePath, "mergerenames_wd");
-            MergeTestRepoWorkingDirPath = Path.Combine(sourceRelativePath, "merge_testrepo_wd");
-            RevertTestRepoWorkingDirPath = Path.Combine(sourceRelativePath, "revert_testrepo_wd");
-            SubmoduleTestRepoWorkingDirPath = Path.Combine(sourceRelativePath, "submodule_wd");
-            SubmoduleTargetTestRepoWorkingDirPath = Path.Combine(sourceRelativePath, "submodule_target_wd");
-            AssumeUnchangedRepoWorkingDirPath = Path.Combine(sourceRelativePath, "assume_unchanged_wd");
-            SubmoduleSmallTestRepoWorkingDirPath = Path.Combine(sourceRelativePath, "submodule_small_wd");
-            PackBuilderTestRepoPath = Path.Combine(sourceRelativePath, "packbuilder_testrepo_wd");
+            ShallowTestRepoPath = Path.Combine(ResourcesDirectory.FullName, "shallow.git");
+            MergedTestRepoWorkingDirPath = Path.Combine(ResourcesDirectory.FullName, "mergedrepo_wd");
+            MergeRenamesTestRepoWorkingDirPath = Path.Combine(ResourcesDirectory.FullName, "mergerenames_wd");
+            MergeTestRepoWorkingDirPath = Path.Combine(ResourcesDirectory.FullName, "merge_testrepo_wd");
+            RevertTestRepoWorkingDirPath = Path.Combine(ResourcesDirectory.FullName, "revert_testrepo_wd");
+            SubmoduleTestRepoWorkingDirPath = Path.Combine(ResourcesDirectory.FullName, "submodule_wd");
+            SubmoduleTargetTestRepoWorkingDirPath = Path.Combine(ResourcesDirectory.FullName, "submodule_target_wd");
+            AssumeUnchangedRepoWorkingDirPath = Path.Combine(ResourcesDirectory.FullName, "assume_unchanged_wd");
+            SubmoduleSmallTestRepoWorkingDirPath = Path.Combine(ResourcesDirectory.FullName, "submodule_small_wd");
+            PackBuilderTestRepoPath = Path.Combine(ResourcesDirectory.FullName, "packbuilder_testrepo_wd");
 
             CleanupTestReposOlderThan(TimeSpan.FromMinutes(15));
         }