Add support for custom smart transports (#806)

This change adds support for git smart transports. This will be then
used to implement http, https, and ssh transports that don't rely on the
libgit2 library.

(cherry picked from commit f1fa96c)

Author: lhchavez

clone.go

@@ -85,6 +85,7 @@ func remoteCreateCallback(
 	// clear finalizer as the calling C function will
 	// free the remote itself
 	runtime.SetFinalizer(remote, nil)
+	remote.repo.Remotes.untrackRemote(remote)
 
 	return C.int(ErrorCodeOK)
 }

git.go

@@ -128,13 +128,15 @@ var (
 type doNotCompare [0]func()
 
 var pointerHandles *HandleList
+var remotePointers *remotePointerList
 
 func init() {
 	initLibGit2()
 }
 
 func initLibGit2() {
 	pointerHandles = NewHandleList()
+	remotePointers = newRemotePointerList()
 
 	C.git_libgit2_init()
 
@@ -160,7 +162,11 @@ func initLibGit2() {
 // After this is called, invoking any function from this library will result in
 // undefined behavior, so make sure this is called carefully.
 func Shutdown() {
+	if err := unregisterManagedTransports(); err != nil {
+		panic(err)
+	}
 	pointerHandles.Clear()
+	remotePointers.clear()
 
 	C.git_libgit2_shutdown()
 }

git_test.go

@@ -13,6 +13,10 @@ import (
 func TestMain(m *testing.M) {
 	ret := m.Run()
 
+	if err := unregisterManagedTransports(); err != nil {
+		panic(err)
+	}
+
 	// Ensure that we are not leaking any pointer handles.
 	pointerHandles.Lock()
 	if len(pointerHandles.handles) > 0 {
@@ -23,6 +27,16 @@ func TestMain(m *testing.M) {
 	}
 	pointerHandles.Unlock()
 
+	// Or remote pointers.
+	remotePointers.Lock()
+	if len(remotePointers.pointers) > 0 {
+		for ptr, remote := range remotePointers.pointers {
+			fmt.Printf("%016p: %+v\n", ptr, remote)
+		}
+		panic("remote pointer list not empty")
+	}
+	remotePointers.Unlock()
+
 	Shutdown()
 
 	os.Exit(ret)

remote.go

@@ -14,6 +14,7 @@ import (
 	"reflect"
 	"runtime"
 	"strings"
+	"sync"
 	"unsafe"
 )
 
@@ -173,6 +174,64 @@ type Remote struct {
 	repo      *Repository
 }
 
+type remotePointerList struct {
+	sync.RWMutex
+	// stores the Go pointers
+	pointers map[*C.git_remote]*Remote
+}
+
+func newRemotePointerList() *remotePointerList {
+	return &remotePointerList{
+		pointers: make(map[*C.git_remote]*Remote),
+	}
+}
+
+// track adds the given pointer to the list of pointers to track and
+// returns a pointer value which can be passed to C as an opaque
+// pointer.
+func (v *remotePointerList) track(remote *Remote) {
+	v.Lock()
+	v.pointers[remote.ptr] = remote
+	v.Unlock()
+
+	runtime.SetFinalizer(remote, (*Remote).Free)
+}
+
+// untrack stops tracking the git_remote pointer.
+func (v *remotePointerList) untrack(remote *Remote) {
+	v.Lock()
+	delete(v.pointers, remote.ptr)
+	v.Unlock()
+}
+
+// clear stops tracking all the git_remote pointers.
+func (v *remotePointerList) clear() {
+	v.Lock()
+	var remotes []*Remote
+	for remotePtr, remote := range v.pointers {
+		remotes = append(remotes, remote)
+		delete(v.pointers, remotePtr)
+	}
+	v.Unlock()
+
+	for _, remote := range remotes {
+		remote.free()
+	}
+}
+
+// get retrieves the pointer from the given *git_remote.
+func (v *remotePointerList) get(ptr *C.git_remote) (*Remote, bool) {
+	v.RLock()
+	defer v.RUnlock()
+
+	r, ok := v.pointers[ptr]
+	if !ok {
+		return nil, false
+	}
+
+	return r, true
+}
+
 type CertificateKind uint
 
 const (
@@ -507,17 +566,42 @@ func RemoteIsValidName(name string) bool {
 	return C.git_remote_is_valid_name(cname) == 1
 }
 
-// Free releases the resources of the Remote.
-func (r *Remote) Free() {
+// free releases the resources of the Remote.
+func (r *Remote) free() {
 	runtime.SetFinalizer(r, nil)
 	C.git_remote_free(r.ptr)
 	r.ptr = nil
 	r.repo = nil
 }
 
+// Free releases the resources of the Remote.
+func (r *Remote) Free() {
+	r.repo.Remotes.untrackRemote(r)
+	r.free()
+}
+
 type RemoteCollection struct {
 	doNotCompare
 	repo *Repository
+
+	sync.RWMutex
+	remotes map[*C.git_remote]*Remote
+}
+
+func (c *RemoteCollection) trackRemote(r *Remote) {
+	c.Lock()
+	c.remotes[r.ptr] = r
+	c.Unlock()
+
+	remotePointers.track(r)
+}
+
+func (c *RemoteCollection) untrackRemote(r *Remote) {
+	c.Lock()
+	delete(c.remotes, r.ptr)
+	c.Unlock()
+
+	remotePointers.untrack(r)
 }
 
 func (c *RemoteCollection) List() ([]string, error) {
@@ -552,7 +636,7 @@ func (c *RemoteCollection) Create(name string, url string) (*Remote, error) {
 	if ret < 0 {
 		return nil, MakeGitError(ret)
 	}
-	runtime.SetFinalizer(remote, (*Remote).Free)
+	c.trackRemote(remote)
 	return remote, nil
 }
 
@@ -568,13 +652,13 @@ func (c *RemoteCollection) CreateWithOptions(url string, option *RemoteCreateOpt
 
 	copts := populateRemoteCreateOptions(&C.git_remote_create_options{}, option, c.repo)
 	defer freeRemoteCreateOptions(copts)
+
 	ret := C.git_remote_create_with_opts(&remote.ptr, curl, copts)
 	runtime.KeepAlive(c.repo)
 	if ret < 0 {
 		return nil, MakeGitError(ret)
 	}
-
-	runtime.SetFinalizer(remote, (*Remote).Free)
+	c.trackRemote(remote)
 	return remote, nil
 }
 
@@ -610,7 +694,7 @@ func (c *RemoteCollection) CreateWithFetchspec(name string, url string, fetch st
 	if ret < 0 {
 		return nil, MakeGitError(ret)
 	}
-	runtime.SetFinalizer(remote, (*Remote).Free)
+	c.trackRemote(remote)
 	return remote, nil
 }
 
@@ -627,7 +711,7 @@ func (c *RemoteCollection) CreateAnonymous(url string) (*Remote, error) {
 	if ret < 0 {
 		return nil, MakeGitError(ret)
 	}
-	runtime.SetFinalizer(remote, (*Remote).Free)
+	c.trackRemote(remote)
 	return remote, nil
 }
 
@@ -644,10 +728,24 @@ func (c *RemoteCollection) Lookup(name string) (*Remote, error) {
 	if ret < 0 {
 		return nil, MakeGitError(ret)
 	}
-	runtime.SetFinalizer(remote, (*Remote).Free)
+	c.trackRemote(remote)
 	return remote, nil
 }
 
+func (c *RemoteCollection) Free() {
+	var remotes []*Remote
+	c.Lock()
+	for remotePtr, remote := range c.remotes {
+		remotes = append(remotes, remote)
+		delete(c.remotes, remotePtr)
+	}
+	c.Unlock()
+
+	for _, remote := range remotes {
+		remotePointers.untrack(remote)
+	}
+}
+
 func (o *Remote) Name() string {
 	s := C.git_remote_name(o.ptr)
 	runtime.KeepAlive(o)

remote_test.go

@@ -97,6 +97,7 @@ func TestRemoteConnectOption(t *testing.T) {
 
 	remote, err := repo.Remotes.CreateWithOptions("https://github.com/libgit2/TestGitRepository", option)
 	checkFatal(t, err)
+	defer remote.Free()
 
 	err = remote.ConnectFetch(nil, nil, nil)
 	checkFatal(t, err)

repository.go

@@ -46,6 +46,7 @@ func newRepositoryFromC(ptr *C.git_repository) *Repository {
 	repo := &Repository{ptr: ptr}
 
 	repo.Remotes.repo = repo
+	repo.Remotes.remotes = make(map[*C.git_remote]*Remote)
 	repo.Submodules.repo = repo
 	repo.References.repo = repo
 	repo.Notes.repo = repo
@@ -144,6 +145,7 @@ func (v *Repository) Free() {
 	ptr := v.ptr
 	v.ptr = nil
 	runtime.SetFinalizer(v, nil)
+	v.Remotes.Free()
 	if v.weak {
 		return
 	}