Allow libgit2# to redirect the global/system/xdg config search path

LibGit2Sharp.Tests/ConfigurationFixture.cs

@@ -431,5 +431,127 @@ public void CannotBuildAProperSignatureFromConfigWhenFullIdentityCannotBeFoundIn
                 Assert.Null(signature);
             }
         }
+
+        [Fact]
+        public void CanSetAndGetSearchPath()
+        {
+            string globalPath = Path.Combine(Constants.TemporaryReposPath, Path.GetRandomFileName());
+            string systemPath = Path.Combine(Constants.TemporaryReposPath, Path.GetRandomFileName());
+            string xdgPath    = Path.Combine(Constants.TemporaryReposPath, Path.GetRandomFileName());
+
+            GlobalSettings.SetConfigSearchPaths(ConfigurationLevel.Global, globalPath);
+            GlobalSettings.SetConfigSearchPaths(ConfigurationLevel.System, systemPath);
+            GlobalSettings.SetConfigSearchPaths(ConfigurationLevel.Xdg,    xdgPath);
+
+            Assert.Equal(globalPath, GlobalSettings.GetConfigSearchPaths(ConfigurationLevel.Global).Single());
+            Assert.Equal(systemPath, GlobalSettings.GetConfigSearchPaths(ConfigurationLevel.System).Single());
+            Assert.Equal(xdgPath,    GlobalSettings.GetConfigSearchPaths(ConfigurationLevel.Xdg).Single());
+
+            // reset the search paths to their defaults
+            GlobalSettings.SetConfigSearchPaths(ConfigurationLevel.Global, null);
+            GlobalSettings.SetConfigSearchPaths(ConfigurationLevel.System, null);
+            GlobalSettings.SetConfigSearchPaths(ConfigurationLevel.Xdg,    null);
+        }
+
+        [Fact]
+        public void CanSetAndGetMultipleSearchPaths()
+        {
+            string[] paths =
+            {
+                Path.Combine(Constants.TemporaryReposPath, Path.GetRandomFileName()),
+                Path.Combine(Constants.TemporaryReposPath, Path.GetRandomFileName()),
+                Path.Combine(Constants.TemporaryReposPath, Path.GetRandomFileName()),
+            };
+
+            GlobalSettings.SetConfigSearchPaths(ConfigurationLevel.Global, paths);
+
+            Assert.Equal(paths, GlobalSettings.GetConfigSearchPaths(ConfigurationLevel.Global));
+
+            // set back to the defaults
+            GlobalSettings.SetConfigSearchPaths(ConfigurationLevel.Global, null);
+        }
+
+        [Fact]
+        public void CanResetSearchPaths()
+        {
+            // all of these calls should reset the config path to the default
+            Action[] resetActions =
+            {
+                () => GlobalSettings.SetConfigSearchPaths(ConfigurationLevel.Global),
+                () => GlobalSettings.SetConfigSearchPaths(ConfigurationLevel.Global, null),
+                () => GlobalSettings.SetConfigSearchPaths(ConfigurationLevel.Global, string.Empty),
+                () => GlobalSettings.SetConfigSearchPaths(ConfigurationLevel.Global, new string[] { }),
+            };
+
+            // record the default search path
+            GlobalSettings.SetConfigSearchPaths(ConfigurationLevel.Global, null);
+            var oldPaths = GlobalSettings.GetConfigSearchPaths(ConfigurationLevel.Global);
+            Assert.NotNull(oldPaths);
+
+            // generate a non-default path to set
+            var newPaths = new string[] { Path.Combine(Constants.TemporaryReposPath, Path.GetRandomFileName()) };
+
+            foreach (var tryToReset in resetActions)
+            {
+                // change to the non-default path
+                GlobalSettings.SetConfigSearchPaths(ConfigurationLevel.Global, newPaths);
+                Assert.Equal(newPaths, GlobalSettings.GetConfigSearchPaths(ConfigurationLevel.Global));
+
+                // set it back to the default
+                tryToReset();
+                Assert.Equal(oldPaths, GlobalSettings.GetConfigSearchPaths(ConfigurationLevel.Global));
+            }
+
+            // make sure the config paths are reset after the test ends
+            GlobalSettings.SetConfigSearchPaths(ConfigurationLevel.Global, null);
+        }
+
+        [Fact]
+        public void CanAppendToSearchPaths()
+        {
+            string appendMe = Path.Combine(Constants.TemporaryReposPath, Path.GetRandomFileName());
+            var prevPaths = GlobalSettings.GetConfigSearchPaths(ConfigurationLevel.Global);
+
+            // append using the special name $PATH
+            GlobalSettings.SetConfigSearchPaths(ConfigurationLevel.Global, "$PATH", appendMe);
+
+            var currentPaths = GlobalSettings.GetConfigSearchPaths(ConfigurationLevel.Global);
+            Assert.Equal(currentPaths, prevPaths.Concat(new[] { appendMe }));
+
+            // set it back to the default
+            GlobalSettings.SetConfigSearchPaths(ConfigurationLevel.Global, null);
+        }
+
+        [Fact]
+        public void CanRedirectConfigAccess()
+        {
+            var scd1 = BuildSelfCleaningDirectory();
+            var scd2 = BuildSelfCleaningDirectory();
+
+            Touch(scd1.RootedDirectoryPath, ".gitconfig");
+            Touch(scd2.RootedDirectoryPath, ".gitconfig");
+
+            // redirect global access to the first path
+            GlobalSettings.SetConfigSearchPaths(ConfigurationLevel.Global, scd1.RootedDirectoryPath);
+
+            // set a value in the first config
+            using (var config = Configuration.BuildFrom(null))
+            {
+                config.Set("luggage.code", 9876, ConfigurationLevel.Global);
+                Assert.Equal(9876, config.Get<int>("luggage.code", ConfigurationLevel.Global).Value);
+            }
+
+            // redirect global config access to path2
+            GlobalSettings.SetConfigSearchPaths(ConfigurationLevel.Global, scd2.RootedDirectoryPath);
+
+            // if the redirect succeeds, the value set in the prior config should not be visible
+            using (var config = Configuration.BuildFrom(null))
+            {
+                Assert.Equal(-1, config.GetValueOrDefault<int>("luggage.code", ConfigurationLevel.Global, -1));
+            }
+
+            // reset the search path to the default
+            GlobalSettings.SetConfigSearchPaths(ConfigurationLevel.Global, null);
+        }
     }
 }

LibGit2Sharp/Core/NativeMethods.cs

@@ -581,6 +581,25 @@ internal static extern int git_filter_unregister(
         [DllImport(libgit2)]
         internal static extern int git_libgit2_features();
 
+        #region git_libgit2_opts
+
+        // Bindings for git_libgit2_opts(int option, ...):
+        // Currently only GIT_OPT_GET_SEARCH_PATH and GIT_OPT_SET_SEARCH_PATH are supported,
+        // but other overloads could be added using a similar pattern.
+        // CallingConvention.Cdecl is used to allow binding the the C varargs signature, and each possible call signature must be enumerated.
+        // __argslist was an option, but is an undocumented feature that should likely not be used here.
+
+        // git_libgit2_opts(GIT_OPT_GET_SEARCH_PATH, int level, git_buf *buf)
+        [DllImport(libgit2, CallingConvention = CallingConvention.Cdecl)]
+        internal static extern int git_libgit2_opts(int option, uint level, GitBuf buf);
+
+        // git_libgit2_opts(GIT_OPT_SET_SEARCH_PATH, int level, const char *path)
+        [DllImport(libgit2, CallingConvention = CallingConvention.Cdecl)]
+        internal static extern int git_libgit2_opts(int option, uint level,
+            [MarshalAs(UnmanagedType.CustomMarshaler, MarshalCookie = UniqueId.UniqueIdentifier, MarshalTypeRef = typeof(StrictUtf8Marshaler))]string path);
+
+        #endregion
+
         [DllImport(libgit2)]
         internal static extern int git_graph_ahead_behind(out UIntPtr ahead, out UIntPtr behind, RepositorySafeHandle repo, ref GitOid one, ref GitOid two);
 

LibGit2Sharp/Core/Proxy.cs

@@ -3193,6 +3193,60 @@ public static BuiltInFeatures git_libgit2_features()
             return (BuiltInFeatures)NativeMethods.git_libgit2_features();
         }
 
+        // C# equivalent of libgit2's git_libgit2_opt_t
+        private enum LibGitOption
+        {
+            GetMWindowSize,        // GIT_OPT_GET_MWINDOW_SIZE
+            SetMWindowSize,        // GIT_OPT_SET_MWINDOW_SIZE
+            GetMWindowMappedLimit, // GIT_OPT_GET_MWINDOW_MAPPED_LIMIT
+            SetMWindowMappedLimit, // GIT_OPT_SET_MWINDOW_MAPPED_LIMIT
+            GetSearchPath,         // GIT_OPT_GET_SEARCH_PATH
+            SetSearchPath,         // GIT_OPT_SET_SEARCH_PATH
+            SetCacheObjectLimit,   // GIT_OPT_SET_CACHE_OBJECT_LIMIT
+            SetCacheMaxSize,       // GIT_OPT_SET_CACHE_MAX_SIZE
+            EnableCaching,         // GIT_OPT_ENABLE_CACHING
+            GetCachedMemory,       // GIT_OPT_GET_CACHED_MEMORY
+            GetTemplatePath,       // GIT_OPT_GET_TEMPLATE_PATH
+            SetTemplatePath,       // GIT_OPT_SET_TEMPLATE_PATH
+            SetSslCertLocations,   // GIT_OPT_SET_SSL_CERT_LOCATIONS
+        }
+
+        /// <summary>
+        /// Get the paths under which libgit2 searches for the configuration file of a given level.
+        /// </summary>
+        /// <param name="level">The level (global/system/XDG) of the config.</param>
+        /// <returns>
+        ///     The paths delimited by 'GIT_PATH_LIST_SEPARATOR' (<see cref="GlobalSettings.PathListSeparator"/>).
+        /// </returns>
+        public static string git_libgit2_opts_get_search_path(ConfigurationLevel level)
+        {
+            string path;
+
+            using (var buf = new GitBuf())
+            {
+                var res = NativeMethods.git_libgit2_opts((int)LibGitOption.GetSearchPath, (uint)level, buf);
+                Ensure.ZeroResult(res);
+
+                path = LaxUtf8Marshaler.FromNative(buf.ptr) ?? string.Empty;
+            }
+
+            return path;
+        }
+
+        /// <summary>
+        /// Set the path(s) under which libgit2 searches for the configuration file of a given level.
+        /// </summary>
+        /// <param name="level">The level (global/system/XDG) of the config.</param>
+        /// <param name="path">
+        ///     A string of paths delimited by 'GIT_PATH_LIST_SEPARATOR' (<see cref="GlobalSettings.PathListSeparator"/>).
+        ///     Pass null to reset the search path to the default.
+        /// </param>
+        public static void git_libgit2_opts_set_search_path(ConfigurationLevel level, string path)
+        {
+            var res = NativeMethods.git_libgit2_opts((int)LibGitOption.SetSearchPath, (uint)level, path);
+            Ensure.ZeroResult(res);
+        }
+
         #endregion
 
         private static ICollection<TResult> git_foreach<T, TResult>(

LibGit2Sharp/GlobalSettings.cs

@@ -2,6 +2,7 @@
 using System.Collections.Generic;
 using System.IO;
 using System.Reflection;
+using System.Collections.Generic;
 using LibGit2Sharp.Core;
 
 namespace LibGit2Sharp
@@ -272,5 +273,32 @@ internal static void DeregisterFilter(Filter filter)
                 DeregisterFilter(registration);
             }
         }
+
+        /// <summary>
+        /// Get the paths under which libgit2 searches for the configuration file of a given level.
+        /// </summary>
+        /// <param name="level">The level (global/system/XDG) of the config.</param>
+        /// <returns>The paths that are searched</returns>
+        public static IEnumerable<string> GetConfigSearchPaths(ConfigurationLevel level)
+        {
+            return Proxy.git_libgit2_opts_get_search_path(level).Split(Path.PathSeparator);
+        }
+
+        /// <summary>
+        /// Set the paths under which libgit2 searches for the configuration file of a given level.
+        ///
+        /// <seealso cref="RepositoryOptions"/>.
+        /// </summary>
+        /// <param name="level">The level (global/system/XDG) of the config.</param>
+        /// <param name="paths">
+        ///     The new search paths to set.
+        ///     Pass null to reset to the default.
+        ///     The special string "$PATH" will be substituted with the current search path.
+        /// </param>
+        public static void SetConfigSearchPaths(ConfigurationLevel level, params string[] paths)
+        {
+            var pathString = (paths == null) ? null : string.Join(Path.PathSeparator.ToString(), paths);
+            Proxy.git_libgit2_opts_set_search_path(level, pathString);
+        }
     }
 }

LibGit2Sharp/RepositoryOptions.cs

@@ -32,6 +32,7 @@ public sealed class RepositoryOptions
         ///   The path has either to lead to an existing valid configuration file,
         ///   or to a non existent configuration file which will be eventually created.
         /// </para>
+        /// <seealso cref="GlobalSettings.SetConfigSearchPaths"/>.
         /// </summary>
         public string GlobalConfigurationLocation { get; set; }
 
@@ -41,6 +42,7 @@ public sealed class RepositoryOptions
         ///   The path has either to lead to an existing valid configuration file,
         ///   or to a non existent configuration file which will be eventually created.
         /// </para>
+        /// <seealso cref="GlobalSettings.SetConfigSearchPaths"/>.
         /// </summary>
         public string XdgConfigurationLocation { get; set; }
 
@@ -50,6 +52,7 @@ public sealed class RepositoryOptions
         ///   The path has to lead to an existing valid configuration file,
         ///   or to a non existent configuration file which will be eventually created.
         /// </para>
+        /// <seealso cref="GlobalSettings.SetConfigSearchPaths"/>.
         /// </summary>
         public string SystemConfigurationLocation { get; set; }