thodg/libgit2

diff --git a/CMakeLists.txt b/CMakeLists.txt
index 6f1a97e..45881d6 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -408,6 +408,17 @@ IF (SONAME)
 ENDIF()
 CONFIGURE_FILE(${CMAKE_CURRENT_SOURCE_DIR}/libgit2.pc.in ${CMAKE_CURRENT_BINARY_DIR}/libgit2.pc @ONLY)
 
+IF (LIBSSH2_FOUND)
+	SET(INCLUDE_LIBSSH2 "#include <libssh2.h>")
+	SET(GIT_SSH_PK_FUNC "typedef LIBSSH2_USERAUTH_PUBLICKEY_SIGN_FUNC((*git_cred_sign_callback));")
+	SET(GIT_SSH_KI_FUNC "typedef LIBSSH2_USERAUTH_KBDINT_RESPONSE_FUNC((*git_cred_ssh_interactive_callback));")
+ELSE ()
+	SET(GIT_SSH_PK_FUNC "typedef int (*git_cred_sign_callback)(void *, unsigned char **, size_t *, const unsigned char *, size_t, void **);")
+	SET(GIT_SSH_KI_FUNC "typedef int (*git_cred_ssh_interactive_callback)(const char *, int, const char *, int, int, const void *, void *, void **);")
+ENDIF ()
+CONFIGURE_FILE(${CMAKE_CURRENT_SOURCE_DIR}/include/git2/transport.h.in ${CMAKE_CURRENT_SOURCE_DIR}/include/git2/transport.h @ONLY)
+
+
 IF (MSVC_IDE)
    # Precompiled headers
    SET_TARGET_PROPERTIES(git2 PROPERTIES COMPILE_FLAGS "/Yuprecompiled.h /FIprecompiled.h")
diff --git a/include/git2/transport.h b/include/git2/transport.h
deleted file mode 100644
index af7812b..0000000
--- a/include/git2/transport.h
+++ /dev/null
@@ -1,543 +0,0 @@
-/*
- * Copyright (C) the libgit2 contributors. All rights reserved.
- *
- * This file is part of libgit2, distributed under the GNU GPL v2 with
- * a Linking Exception. For full terms see the included COPYING file.
- */
-#ifndef INCLUDE_git_transport_h__
-#define INCLUDE_git_transport_h__
-
-#include "indexer.h"
-#include "net.h"
-#include "types.h"
-
-#ifdef GIT_SSH
-#include <libssh2.h>
-#endif
-
-/**
- * @file git2/transport.h
- * @brief Git transport interfaces and functions
- * @defgroup git_transport interfaces and functions
- * @ingroup Git
- * @{
- */
-GIT_BEGIN_DECL
-
-/*
- *** Begin interface for credentials acquisition ***
- */
-
-/** Authentication type requested */
-typedef enum {
-	/* git_cred_userpass_plaintext */
-	GIT_CREDTYPE_USERPASS_PLAINTEXT = (1u << 0),
-
-	/* git_cred_ssh_key */
-	GIT_CREDTYPE_SSH_KEY = (1u << 1),
-
-	/* git_cred_ssh_custom */
-	GIT_CREDTYPE_SSH_CUSTOM = (1u << 2),
-
-	/* git_cred_default */
-	GIT_CREDTYPE_DEFAULT = (1u << 3),
-
-	/* git_cred_ssh_interactive */
-	GIT_CREDTYPE_SSH_INTERACTIVE = (1u << 4),
-} git_credtype_t;
-
-/* The base structure for all credential types */
-typedef struct git_cred git_cred;
-
-struct git_cred {
-	git_credtype_t credtype;
-	void (*free)(git_cred *cred);
-};
-
-/** A plaintext username and password */
-typedef struct {
-	git_cred parent;
-	char *username;
-	char *password;
-} git_cred_userpass_plaintext;
-
-#ifdef GIT_SSH
-typedef LIBSSH2_USERAUTH_PUBLICKEY_SIGN_FUNC((*git_cred_sign_callback));
-typedef LIBSSH2_USERAUTH_KBDINT_RESPONSE_FUNC((*git_cred_ssh_interactive_callback));
-#else
-typedef int (*git_cred_sign_callback)(void *, ...);
-typedef int (*git_cred_ssh_interactive_callback)(void *, ...);
-#endif
-
-/**
- * A ssh key from disk
- */
-typedef struct git_cred_ssh_key {
-	git_cred parent;
-	char *username;
-	char *publickey;
-	char *privatekey;
-	char *passphrase;
-} git_cred_ssh_key;
-
-/**
- * Keyboard-interactive based ssh authentication
- */
-typedef struct git_cred_ssh_interactive {
-	git_cred parent;
-	char *username;
-	git_cred_ssh_interactive_callback prompt_callback;
-	void *payload;
-} git_cred_ssh_interactive;
-
-/**
- * A key with a custom signature function
- */
-typedef struct git_cred_ssh_custom {
-	git_cred parent;
-	char *username;
-	char *publickey;
-	size_t publickey_len;
-	git_cred_sign_callback sign_callback;
-	void *payload;
-} git_cred_ssh_custom;
-
-/** A key for NTLM/Kerberos "default" credentials */
-typedef struct git_cred git_cred_default;
-
-/**
- * Check whether a credential object contains username information.
- *
- * @param cred object to check
- * @return 1 if the credential object has non-NULL username, 0 otherwise
- */
-GIT_EXTERN(int) git_cred_has_username(git_cred *cred);
-
-/**
- * Create a new plain-text username and password credential object.
- * The supplied credential parameter will be internally duplicated.
- *
- * @param out The newly created credential object.
- * @param username The username of the credential.
- * @param password The password of the credential.
- * @return 0 for success or an error code for failure
- */
-GIT_EXTERN(int) git_cred_userpass_plaintext_new(
-	git_cred **out,
-	const char *username,
-	const char *password);
-
-/**
- * Create a new passphrase-protected ssh key credential object.
- * The supplied credential parameter will be internally duplicated.
- *
- * @param out The newly created credential object.
- * @param username username to use to authenticate
- * @param publickey The path to the public key of the credential.
- * @param privatekey The path to the private key of the credential.
- * @param passphrase The passphrase of the credential.
- * @return 0 for success or an error code for failure
- */
-GIT_EXTERN(int) git_cred_ssh_key_new(
-	git_cred **out,
-	const char *username,
-	const char *publickey,
-	const char *privatekey,
-	const char *passphrase);
-
-/**
- * Create a new ssh keyboard-interactive based credential object.
- * The supplied credential parameter will be internally duplicated.
- *
- * @param username Username to use to authenticate.
- * @param prompt_callback The callback method used for prompts.
- * @param payload Additional data to pass to the callback.
- * @return 0 for success or an error code for failure.
- */
-GIT_EXTERN(int) git_cred_ssh_interactive_new(
-	git_cred **out,
-	const char *username,
-	git_cred_ssh_interactive_callback prompt_callback,
-	void *payload);
-
-/**
- * Create a new ssh key credential object used for querying an ssh-agent.
- * The supplied credential parameter will be internally duplicated.
- *
- * @param out The newly created credential object.
- * @param username username to use to authenticate
- * @return 0 for success or an error code for failure
- */
-GIT_EXTERN(int) git_cred_ssh_key_from_agent(
-	git_cred **out,
-	const char *username);
-
-/**
- * Create an ssh key credential with a custom signing function.
- *
- * This lets you use your own function to sign the challenge.
- *
- * This function and its credential type is provided for completeness
- * and wraps `libssh2_userauth_publickey()`, which is undocumented.
- *
- * The supplied credential parameter will be internally duplicated.
- *
- * @param out The newly created credential object.
- * @param username username to use to authenticate
- * @param publickey The bytes of the public key.
- * @param publickey_len The length of the public key in bytes.
- * @param sign_callback The callback method to sign the data during the challenge.
- * @param payload Additional data to pass to the callback.
- * @return 0 for success or an error code for failure
- */
-GIT_EXTERN(int) git_cred_ssh_custom_new(
-	git_cred **out,
-	const char *username,
-	const char *publickey,
-	size_t publickey_len,
-	git_cred_sign_callback sign_callback,
-	void *payload);
-
-/**
- * Create a "default" credential usable for Negotiate mechanisms like NTLM
- * or Kerberos authentication.
- *
- * @return 0 for success or an error code for failure
- */
-GIT_EXTERN(int) git_cred_default_new(git_cred **out);
-
-/**
- * Signature of a function which acquires a credential object.
- *
- * - cred: The newly created credential object.
- * - url: The resource for which we are demanding a credential.
- * - username_from_url: The username that was embedded in a "user@host"
- *                          remote url, or NULL if not included.
- * - allowed_types: A bitmask stating which cred types are OK to return.
- * - payload: The payload provided when specifying this callback.
- * - returns 0 for success, < 0 to indicate an error, > 0 to indicate
- *       no credential was acquired
- */
-typedef int (*git_cred_acquire_cb)(
-	git_cred **cred,
-	const char *url,
-	const char *username_from_url,
-	unsigned int allowed_types,
-	void *payload);
-
-/*
- *** End interface for credentials acquisition ***
- *** Begin base transport interface ***
- */
-
-typedef enum {
-	GIT_TRANSPORTFLAGS_NONE = 0,
-	/* If the connection is secured with SSL/TLS, the authenticity
-	 * of the server certificate should not be verified. */
-	GIT_TRANSPORTFLAGS_NO_CHECK_CERT = 1
-} git_transport_flags_t;
-
-typedef int (*git_transport_message_cb)(const char *str, int len, void *data);
-
-typedef struct git_transport git_transport;
-
-struct git_transport {
-	unsigned int version;
-	/* Set progress and error callbacks */
-	int (*set_callbacks)(
-		git_transport *transport,
-		git_transport_message_cb progress_cb,
-		git_transport_message_cb error_cb,
-		void *payload);
-
-	/* Connect the transport to the remote repository, using the given
-	 * direction. */
-	int (*connect)(
-		git_transport *transport,
-		const char *url,
-		git_cred_acquire_cb cred_acquire_cb,
-		void *cred_acquire_payload,
-		int direction,
-		int flags);
-
-	/* This function may be called after a successful call to
-	 * connect(). The array returned is owned by the transport and
-	 * is guranteed until the next call of a transport function. */
-	int (*ls)(
-		const git_remote_head ***out,
-		size_t *size,
-		git_transport *transport);
-
-	/* Executes the push whose context is in the git_push object. */
-	int (*push)(git_transport *transport, git_push *push);
-
-	/* This function may be called after a successful call to connect(), when
-	 * the direction is FETCH. The function performs a negotiation to calculate
-	 * the wants list for the fetch. */
-	int (*negotiate_fetch)(
-		git_transport *transport,
-		git_repository *repo,
-		const git_remote_head * const *refs,
-		size_t count);
-
-	/* This function may be called after a successful call to negotiate_fetch(),
-	 * when the direction is FETCH. This function retrieves the pack file for
-	 * the fetch from the remote end. */
-	int (*download_pack)(
-		git_transport *transport,
-		git_repository *repo,
-		git_transfer_progress *stats,
-		git_transfer_progress_cb progress_cb,
-		void *progress_payload);
-
-	/* Checks to see if the transport is connected */
-	int (*is_connected)(git_transport *transport);
-
-	/* Reads the flags value previously passed into connect() */
-	int (*read_flags)(git_transport *transport, int *flags);
-
-	/* Cancels any outstanding transport operation */
-	void (*cancel)(git_transport *transport);
-
-	/* This function is the reverse of connect() -- it terminates the
-	 * connection to the remote end. */
-	int (*close)(git_transport *transport);
-
-	/* Frees/destructs the git_transport object. */
-	void (*free)(git_transport *transport);
-};
-
-#define GIT_TRANSPORT_VERSION 1
-#define GIT_TRANSPORT_INIT {GIT_TRANSPORT_VERSION}
-
-/**
- * Initializes a `git_transport` with default values. Equivalent to
- * creating an instance with GIT_TRANSPORT_INIT.
- *
- * @param opts the `git_transport` struct to initialize
- * @param version Version of struct; pass `GIT_TRANSPORT_VERSION`
- * @return Zero on success; -1 on failure.
- */
-GIT_EXTERN(int) git_transport_init(
-	git_transport *opts,
-	unsigned int version);
-
-/**
- * Function to use to create a transport from a URL. The transport database
- * is scanned to find a transport that implements the scheme of the URI (i.e.
- * git:// or http://) and a transport object is returned to the caller.
- *
- * @param out The newly created transport (out)
- * @param owner The git_remote which will own this transport
- * @param url The URL to connect to
- * @return 0 or an error code
- */
-GIT_EXTERN(int) git_transport_new(git_transport **out, git_remote *owner, const char *url);
-
-/* Signature of a function which creates a transport */
-typedef int (*git_transport_cb)(git_transport **out, git_remote *owner, void *param);
-
-/**
- * Add a custom transport definition, to be used in addition to the built-in
- * set of transports that come with libgit2.
- *
- * The caller is responsible for synchronizing calls to git_transport_register
- * and git_transport_unregister with other calls to the library that
- * instantiate transports.
- *
- * @param prefix The scheme (ending in "://") to match, i.e. "git://"
- * @param priority The priority of this transport relative to others with
- *		the same prefix. Built-in transports have a priority of 1.
- * @param cb The callback used to create an instance of the transport
- * @param param A fixed parameter to pass to cb at creation time
- * @return 0 or an error code
- */
-GIT_EXTERN(int) git_transport_register(
-	const char *prefix,
-	unsigned priority,
-	git_transport_cb cb,
-	void *param);
-
-/**
- *
- * Unregister a custom transport definition which was previously registered
- * with git_transport_register.
- *
- * @param prefix From the previous call to git_transport_register
- * @param priority From the previous call to git_transport_register
- * @return 0 or an error code
- */
-GIT_EXTERN(int) git_transport_unregister(
-	const char *prefix,
-	unsigned priority);
-
-/* Transports which come with libgit2 (match git_transport_cb). The expected
- * value for "param" is listed in-line below. */
-
-/**
- * Create an instance of the dummy transport.
- *
- * @param out The newly created transport (out)
- * @param owner The git_remote which will own this transport
- * @param payload You must pass NULL for this parameter.
- * @return 0 or an error code
- */
-GIT_EXTERN(int) git_transport_dummy(
-	git_transport **out,
-	git_remote *owner,
-	/* NULL */ void *payload);
-
-/**
- * Create an instance of the local transport.
- *
- * @param out The newly created transport (out)
- * @param owner The git_remote which will own this transport
- * @param payload You must pass NULL for this parameter.
- * @return 0 or an error code
- */
-GIT_EXTERN(int) git_transport_local(
-	git_transport **out,
-	git_remote *owner,
-	/* NULL */ void *payload);
-
-/**
- * Create an instance of the smart transport.
- *
- * @param out The newly created transport (out)
- * @param owner The git_remote which will own this transport
- * @param payload A pointer to a git_smart_subtransport_definition
- * @return 0 or an error code
- */
-GIT_EXTERN(int) git_transport_smart(
-	git_transport **out,
-	git_remote *owner,
-	/* (git_smart_subtransport_definition *) */ void *payload);
-
-/*
- *** End of base transport interface ***
- *** Begin interface for subtransports for the smart transport ***
- */
-
-/* The smart transport knows how to speak the git protocol, but it has no
- * knowledge of how to establish a connection between it and another endpoint,
- * or how to move data back and forth. For this, a subtransport interface is
- * declared, and the smart transport delegates this work to the subtransports.
- * Three subtransports are implemented: git, http, and winhttp. (The http and
- * winhttp transports each implement both http and https.) */
-
-/* Subtransports can either be RPC = 0 (persistent connection) or RPC = 1
- * (request/response). The smart transport handles the differences in its own
- * logic. The git subtransport is RPC = 0, while http and winhttp are both
- * RPC = 1. */
-
-/* Actions that the smart transport can ask
- * a subtransport to perform */
-typedef enum {
-	GIT_SERVICE_UPLOADPACK_LS = 1,
-	GIT_SERVICE_UPLOADPACK = 2,
-	GIT_SERVICE_RECEIVEPACK_LS = 3,
-	GIT_SERVICE_RECEIVEPACK = 4,
-} git_smart_service_t;
-
-typedef struct git_smart_subtransport git_smart_subtransport;
-typedef struct git_smart_subtransport_stream git_smart_subtransport_stream;
-
-/* A stream used by the smart transport to read and write data
- * from a subtransport */
-struct git_smart_subtransport_stream {
-	/* The owning subtransport */
-	git_smart_subtransport *subtransport;
-
-	int (*read)(
-		git_smart_subtransport_stream *stream,
-		char *buffer,
-		size_t buf_size,
-		size_t *bytes_read);
-
-	int (*write)(
-		git_smart_subtransport_stream *stream,
-		const char *buffer,
-		size_t len);
-
-	void (*free)(
-		git_smart_subtransport_stream *stream);
-};
-
-/* An implementation of a subtransport which carries data for the
- * smart transport */
-struct git_smart_subtransport {
-	int (* action)(
-			git_smart_subtransport_stream **out,
-			git_smart_subtransport *transport,
-			const char *url,
-			git_smart_service_t action);
-
-	/* Subtransports are guaranteed a call to close() between
-	 * calls to action(), except for the following two "natural" progressions
-	 * of actions against a constant URL.
-	 *
-	 * 1. UPLOADPACK_LS -> UPLOADPACK
-	 * 2. RECEIVEPACK_LS -> RECEIVEPACK */
-	int (*close)(git_smart_subtransport *transport);
-
-	void (*free)(git_smart_subtransport *transport);
-};
-
-/* A function which creates a new subtransport for the smart transport */
-typedef int (*git_smart_subtransport_cb)(
-	git_smart_subtransport **out,
-	git_transport* owner);
-
-typedef struct git_smart_subtransport_definition {
-	/* The function to use to create the git_smart_subtransport */
-	git_smart_subtransport_cb callback;
-
-	/* True if the protocol is stateless; false otherwise. For example,
-	 * http:// is stateless, but git:// is not. */
-	unsigned rpc;
-} git_smart_subtransport_definition;
-
-/* Smart transport subtransports that come with libgit2 */
-
-/**
- * Create an instance of the http subtransport. This subtransport
- * also supports https. On Win32, this subtransport may be implemented
- * using the WinHTTP library.
- *
- * @param out The newly created subtransport
- * @param owner The smart transport to own this subtransport
- * @return 0 or an error code
- */
-GIT_EXTERN(int) git_smart_subtransport_http(
-	git_smart_subtransport **out,
-	git_transport* owner);
-
-/**
- * Create an instance of the git subtransport.
- *
- * @param out The newly created subtransport
- * @param owner The smart transport to own this subtransport
- * @return 0 or an error code
- */
-GIT_EXTERN(int) git_smart_subtransport_git(
-	git_smart_subtransport **out,
-	git_transport* owner);
-
-/**
- * Create an instance of the ssh subtransport.
- *
- * @param out The newly created subtransport
- * @param owner The smart transport to own this subtransport
- * @return 0 or an error code
- */
-GIT_EXTERN(int) git_smart_subtransport_ssh(
-	git_smart_subtransport **out,
-	git_transport* owner);
-
-/*
- *** End interface for subtransports for the smart transport ***
- */
-
-/** @} */
-GIT_END_DECL
-#endif
diff --git a/include/git2/transport.h.in b/include/git2/transport.h.in
new file mode 100644
index 0000000..73f0a99
--- /dev/null
+++ b/include/git2/transport.h.in
@@ -0,0 +1,542 @@
+/*
+ * Copyright (C) the libgit2 contributors. All rights reserved.
+ *
+ * This file is part of libgit2, distributed under the GNU GPL v2 with
+ * a Linking Exception. For full terms see the included COPYING file.
+ */
+#ifndef INCLUDE_git_transport_h__
+#define INCLUDE_git_transport_h__
+
+#include "indexer.h"
+#include "net.h"
+#include "types.h"
+
+@INCLUDE_LIBSSH2@
+
+/**
+ * @file git2/transport.h
+ * @brief Git transport interfaces and functions
+ * @defgroup git_transport interfaces and functions
+ * @ingroup Git
+ * @{
+ */
+GIT_BEGIN_DECL
+
+/*
+ *** Begin interface for credentials acquisition ***
+ */
+
+/** Authentication type requested */
+typedef enum {
+	/* git_cred_userpass_plaintext */
+	GIT_CREDTYPE_USERPASS_PLAINTEXT = (1u << 0),
+
+	/* git_cred_ssh_key */
+	GIT_CREDTYPE_SSH_KEY = (1u << 1),
+
+	/* git_cred_ssh_custom */
+	GIT_CREDTYPE_SSH_CUSTOM = (1u << 2),
+
+	/* git_cred_default */
+	GIT_CREDTYPE_DEFAULT = (1u << 3),
+
+	/* git_cred_ssh_interactive */
+	GIT_CREDTYPE_SSH_INTERACTIVE = (1u << 4),
+} git_credtype_t;
+
+/* The base structure for all credential types */
+typedef struct git_cred git_cred;
+
+struct git_cred {
+	git_credtype_t credtype;
+	void (*free)(git_cred *cred);
+};
+
+/** A plaintext username and password */
+typedef struct {
+	git_cred parent;
+	char *username;
+	char *password;
+} git_cred_userpass_plaintext;
+
+/*
+ * This defines the callbacks for custom public key signatures and
+ * keyboard-interactive authentication. It is replaced at build-time
+ * with either the libssh2 signature or a dummy signature that's close
+ * enough but with void pointers instead of libssh2 structures.
+ */
+@GIT_SSH_PK_FUNC@
+@GIT_SSH_KI_FUNC@
+
+/**
+ * A ssh key from disk
+ */
+typedef struct git_cred_ssh_key {
+	git_cred parent;
+	char *username;
+	char *publickey;
+	char *privatekey;
+	char *passphrase;
+} git_cred_ssh_key;
+
+/**
+ * Keyboard-interactive based ssh authentication
+ */
+typedef struct git_cred_ssh_interactive {
+	git_cred parent;
+	char *username;
+	git_cred_ssh_interactive_callback prompt_callback;
+	void *payload;
+} git_cred_ssh_interactive;
+
+/**
+ * A key with a custom signature function
+ */
+typedef struct git_cred_ssh_custom {
+	git_cred parent;
+	char *username;
+	char *publickey;
+	size_t publickey_len;
+	git_cred_sign_callback sign_callback;
+	void *payload;
+} git_cred_ssh_custom;
+
+/** A key for NTLM/Kerberos "default" credentials */
+typedef struct git_cred git_cred_default;
+
+/**
+ * Check whether a credential object contains username information.
+ *
+ * @param cred object to check
+ * @return 1 if the credential object has non-NULL username, 0 otherwise
+ */
+GIT_EXTERN(int) git_cred_has_username(git_cred *cred);
+
+/**
+ * Create a new plain-text username and password credential object.
+ * The supplied credential parameter will be internally duplicated.
+ *
+ * @param out The newly created credential object.
+ * @param username The username of the credential.
+ * @param password The password of the credential.
+ * @return 0 for success or an error code for failure
+ */
+GIT_EXTERN(int) git_cred_userpass_plaintext_new(
+	git_cred **out,
+	const char *username,
+	const char *password);
+
+/**
+ * Create a new passphrase-protected ssh key credential object.
+ * The supplied credential parameter will be internally duplicated.
+ *
+ * @param out The newly created credential object.
+ * @param username username to use to authenticate
+ * @param publickey The path to the public key of the credential.
+ * @param privatekey The path to the private key of the credential.
+ * @param passphrase The passphrase of the credential.
+ * @return 0 for success or an error code for failure
+ */
+GIT_EXTERN(int) git_cred_ssh_key_new(
+	git_cred **out,
+	const char *username,
+	const char *publickey,
+	const char *privatekey,
+	const char *passphrase);
+
+/**
+ * Create a new ssh keyboard-interactive based credential object.
+ * The supplied credential parameter will be internally duplicated.
+ *
+ * @param username Username to use to authenticate.
+ * @param prompt_callback The callback method used for prompts.
+ * @param payload Additional data to pass to the callback.
+ * @return 0 for success or an error code for failure.
+ */
+GIT_EXTERN(int) git_cred_ssh_interactive_new(
+	git_cred **out,
+	const char *username,
+	git_cred_ssh_interactive_callback prompt_callback,
+	void *payload);
+
+/**
+ * Create a new ssh key credential object used for querying an ssh-agent.
+ * The supplied credential parameter will be internally duplicated.
+ *
+ * @param out The newly created credential object.
+ * @param username username to use to authenticate
+ * @return 0 for success or an error code for failure
+ */
+GIT_EXTERN(int) git_cred_ssh_key_from_agent(
+	git_cred **out,
+	const char *username);
+
+/**
+ * Create an ssh key credential with a custom signing function.
+ *
+ * This lets you use your own function to sign the challenge.
+ *
+ * This function and its credential type is provided for completeness
+ * and wraps `libssh2_userauth_publickey()`, which is undocumented.
+ *
+ * The supplied credential parameter will be internally duplicated.
+ *
+ * @param out The newly created credential object.
+ * @param username username to use to authenticate
+ * @param publickey The bytes of the public key.
+ * @param publickey_len The length of the public key in bytes.
+ * @param sign_callback The callback method to sign the data during the challenge.
+ * @param payload Additional data to pass to the callback.
+ * @return 0 for success or an error code for failure
+ */
+GIT_EXTERN(int) git_cred_ssh_custom_new(
+	git_cred **out,
+	const char *username,
+	const char *publickey,
+	size_t publickey_len,
+	git_cred_sign_callback sign_callback,
+	void *payload);
+
+/**
+ * Create a "default" credential usable for Negotiate mechanisms like NTLM
+ * or Kerberos authentication.
+ *
+ * @return 0 for success or an error code for failure
+ */
+GIT_EXTERN(int) git_cred_default_new(git_cred **out);
+
+/**
+ * Signature of a function which acquires a credential object.
+ *
+ * - cred: The newly created credential object.
+ * - url: The resource for which we are demanding a credential.
+ * - username_from_url: The username that was embedded in a "user@host"
+ *                          remote url, or NULL if not included.
+ * - allowed_types: A bitmask stating which cred types are OK to return.
+ * - payload: The payload provided when specifying this callback.
+ * - returns 0 for success, < 0 to indicate an error, > 0 to indicate
+ *       no credential was acquired
+ */
+typedef int (*git_cred_acquire_cb)(
+	git_cred **cred,
+	const char *url,
+	const char *username_from_url,
+	unsigned int allowed_types,
+	void *payload);
+
+/*
+ *** End interface for credentials acquisition ***
+ *** Begin base transport interface ***
+ */
+
+typedef enum {
+	GIT_TRANSPORTFLAGS_NONE = 0,
+	/* If the connection is secured with SSL/TLS, the authenticity
+	 * of the server certificate should not be verified. */
+	GIT_TRANSPORTFLAGS_NO_CHECK_CERT = 1
+} git_transport_flags_t;
+
+typedef int (*git_transport_message_cb)(const char *str, int len, void *data);
+
+typedef struct git_transport git_transport;
+
+struct git_transport {
+	unsigned int version;
+	/* Set progress and error callbacks */
+	int (*set_callbacks)(
+		git_transport *transport,
+		git_transport_message_cb progress_cb,
+		git_transport_message_cb error_cb,
+		void *payload);
+
+	/* Connect the transport to the remote repository, using the given
+	 * direction. */
+	int (*connect)(
+		git_transport *transport,
+		const char *url,
+		git_cred_acquire_cb cred_acquire_cb,
+		void *cred_acquire_payload,
+		int direction,
+		int flags);
+
+	/* This function may be called after a successful call to
+	 * connect(). The array returned is owned by the transport and
+	 * is guranteed until the next call of a transport function. */
+	int (*ls)(
+		const git_remote_head ***out,
+		size_t *size,
+		git_transport *transport);
+
+	/* Executes the push whose context is in the git_push object. */
+	int (*push)(git_transport *transport, git_push *push);
+
+	/* This function may be called after a successful call to connect(), when
+	 * the direction is FETCH. The function performs a negotiation to calculate
+	 * the wants list for the fetch. */
+	int (*negotiate_fetch)(
+		git_transport *transport,
+		git_repository *repo,
+		const git_remote_head * const *refs,
+		size_t count);
+
+	/* This function may be called after a successful call to negotiate_fetch(),
+	 * when the direction is FETCH. This function retrieves the pack file for
+	 * the fetch from the remote end. */
+	int (*download_pack)(
+		git_transport *transport,
+		git_repository *repo,
+		git_transfer_progress *stats,
+		git_transfer_progress_cb progress_cb,
+		void *progress_payload);
+
+	/* Checks to see if the transport is connected */
+	int (*is_connected)(git_transport *transport);
+
+	/* Reads the flags value previously passed into connect() */
+	int (*read_flags)(git_transport *transport, int *flags);
+
+	/* Cancels any outstanding transport operation */
+	void (*cancel)(git_transport *transport);
+
+	/* This function is the reverse of connect() -- it terminates the
+	 * connection to the remote end. */
+	int (*close)(git_transport *transport);
+
+	/* Frees/destructs the git_transport object. */
+	void (*free)(git_transport *transport);
+};
+
+#define GIT_TRANSPORT_VERSION 1
+#define GIT_TRANSPORT_INIT {GIT_TRANSPORT_VERSION}
+
+/**
+ * Initializes a `git_transport` with default values. Equivalent to
+ * creating an instance with GIT_TRANSPORT_INIT.
+ *
+ * @param opts the `git_transport` struct to initialize
+ * @param version Version of struct; pass `GIT_TRANSPORT_VERSION`
+ * @return Zero on success; -1 on failure.
+ */
+GIT_EXTERN(int) git_transport_init(
+	git_transport *opts,
+	unsigned int version);
+
+/**
+ * Function to use to create a transport from a URL. The transport database
+ * is scanned to find a transport that implements the scheme of the URI (i.e.
+ * git:// or http://) and a transport object is returned to the caller.
+ *
+ * @param out The newly created transport (out)
+ * @param owner The git_remote which will own this transport
+ * @param url The URL to connect to
+ * @return 0 or an error code
+ */
+GIT_EXTERN(int) git_transport_new(git_transport **out, git_remote *owner, const char *url);
+
+/* Signature of a function which creates a transport */
+typedef int (*git_transport_cb)(git_transport **out, git_remote *owner, void *param);
+
+/**
+ * Add a custom transport definition, to be used in addition to the built-in
+ * set of transports that come with libgit2.
+ *
+ * The caller is responsible for synchronizing calls to git_transport_register
+ * and git_transport_unregister with other calls to the library that
+ * instantiate transports.
+ *
+ * @param prefix The scheme (ending in "://") to match, i.e. "git://"
+ * @param priority The priority of this transport relative to others with
+ *		the same prefix. Built-in transports have a priority of 1.
+ * @param cb The callback used to create an instance of the transport
+ * @param param A fixed parameter to pass to cb at creation time
+ * @return 0 or an error code
+ */
+GIT_EXTERN(int) git_transport_register(
+	const char *prefix,
+	unsigned priority,
+	git_transport_cb cb,
+	void *param);
+
+/**
+ *
+ * Unregister a custom transport definition which was previously registered
+ * with git_transport_register.
+ *
+ * @param prefix From the previous call to git_transport_register
+ * @param priority From the previous call to git_transport_register
+ * @return 0 or an error code
+ */
+GIT_EXTERN(int) git_transport_unregister(
+	const char *prefix,
+	unsigned priority);
+
+/* Transports which come with libgit2 (match git_transport_cb). The expected
+ * value for "param" is listed in-line below. */
+
+/**
+ * Create an instance of the dummy transport.
+ *
+ * @param out The newly created transport (out)
+ * @param owner The git_remote which will own this transport
+ * @param payload You must pass NULL for this parameter.
+ * @return 0 or an error code
+ */
+GIT_EXTERN(int) git_transport_dummy(
+	git_transport **out,
+	git_remote *owner,
+	/* NULL */ void *payload);
+
+/**
+ * Create an instance of the local transport.
+ *
+ * @param out The newly created transport (out)
+ * @param owner The git_remote which will own this transport
+ * @param payload You must pass NULL for this parameter.
+ * @return 0 or an error code
+ */
+GIT_EXTERN(int) git_transport_local(
+	git_transport **out,
+	git_remote *owner,
+	/* NULL */ void *payload);
+
+/**
+ * Create an instance of the smart transport.
+ *
+ * @param out The newly created transport (out)
+ * @param owner The git_remote which will own this transport
+ * @param payload A pointer to a git_smart_subtransport_definition
+ * @return 0 or an error code
+ */
+GIT_EXTERN(int) git_transport_smart(
+	git_transport **out,
+	git_remote *owner,
+	/* (git_smart_subtransport_definition *) */ void *payload);
+
+/*
+ *** End of base transport interface ***
+ *** Begin interface for subtransports for the smart transport ***
+ */
+
+/* The smart transport knows how to speak the git protocol, but it has no
+ * knowledge of how to establish a connection between it and another endpoint,
+ * or how to move data back and forth. For this, a subtransport interface is
+ * declared, and the smart transport delegates this work to the subtransports.
+ * Three subtransports are implemented: git, http, and winhttp. (The http and
+ * winhttp transports each implement both http and https.) */
+
+/* Subtransports can either be RPC = 0 (persistent connection) or RPC = 1
+ * (request/response). The smart transport handles the differences in its own
+ * logic. The git subtransport is RPC = 0, while http and winhttp are both
+ * RPC = 1. */
+
+/* Actions that the smart transport can ask
+ * a subtransport to perform */
+typedef enum {
+	GIT_SERVICE_UPLOADPACK_LS = 1,
+	GIT_SERVICE_UPLOADPACK = 2,
+	GIT_SERVICE_RECEIVEPACK_LS = 3,
+	GIT_SERVICE_RECEIVEPACK = 4,
+} git_smart_service_t;
+
+typedef struct git_smart_subtransport git_smart_subtransport;
+typedef struct git_smart_subtransport_stream git_smart_subtransport_stream;
+
+/* A stream used by the smart transport to read and write data
+ * from a subtransport */
+struct git_smart_subtransport_stream {
+	/* The owning subtransport */
+	git_smart_subtransport *subtransport;
+
+	int (*read)(
+		git_smart_subtransport_stream *stream,
+		char *buffer,
+		size_t buf_size,
+		size_t *bytes_read);
+
+	int (*write)(
+		git_smart_subtransport_stream *stream,
+		const char *buffer,
+		size_t len);
+
+	void (*free)(
+		git_smart_subtransport_stream *stream);
+};
+
+/* An implementation of a subtransport which carries data for the
+ * smart transport */
+struct git_smart_subtransport {
+	int (* action)(
+			git_smart_subtransport_stream **out,
+			git_smart_subtransport *transport,
+			const char *url,
+			git_smart_service_t action);
+
+	/* Subtransports are guaranteed a call to close() between
+	 * calls to action(), except for the following two "natural" progressions
+	 * of actions against a constant URL.
+	 *
+	 * 1. UPLOADPACK_LS -> UPLOADPACK
+	 * 2. RECEIVEPACK_LS -> RECEIVEPACK */
+	int (*close)(git_smart_subtransport *transport);
+
+	void (*free)(git_smart_subtransport *transport);
+};
+
+/* A function which creates a new subtransport for the smart transport */
+typedef int (*git_smart_subtransport_cb)(
+	git_smart_subtransport **out,
+	git_transport* owner);
+
+typedef struct git_smart_subtransport_definition {
+	/* The function to use to create the git_smart_subtransport */
+	git_smart_subtransport_cb callback;
+
+	/* True if the protocol is stateless; false otherwise. For example,
+	 * http:// is stateless, but git:// is not. */
+	unsigned rpc;
+} git_smart_subtransport_definition;
+
+/* Smart transport subtransports that come with libgit2 */
+
+/**
+ * Create an instance of the http subtransport. This subtransport
+ * also supports https. On Win32, this subtransport may be implemented
+ * using the WinHTTP library.
+ *
+ * @param out The newly created subtransport
+ * @param owner The smart transport to own this subtransport
+ * @return 0 or an error code
+ */
+GIT_EXTERN(int) git_smart_subtransport_http(
+	git_smart_subtransport **out,
+	git_transport* owner);
+
+/**
+ * Create an instance of the git subtransport.
+ *
+ * @param out The newly created subtransport
+ * @param owner The smart transport to own this subtransport
+ * @return 0 or an error code
+ */
+GIT_EXTERN(int) git_smart_subtransport_git(
+	git_smart_subtransport **out,
+	git_transport* owner);
+
+/**
+ * Create an instance of the ssh subtransport.
+ *
+ * @param out The newly created subtransport
+ * @param owner The smart transport to own this subtransport
+ * @return 0 or an error code
+ */
+GIT_EXTERN(int) git_smart_subtransport_ssh(
+	git_smart_subtransport **out,
+	git_transport* owner);
+
+/*
+ *** End interface for subtransports for the smart transport ***
+ */
+
+/** @} */
+GIT_END_DECL
+#endif