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.

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

@@ -15,6 +15,7 @@ import (
 	"reflect"
 	"runtime"
 	"strings"
+	"sync"
 	"unsafe"
 )
 
@@ -174,6 +175,64 @@ 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 (
@@ -509,17 +568,42 @@ 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) {
@@ -554,7 +638,7 @@ 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
 }
 
@@ -570,13 +654,13 @@ 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
 }
 
@@ -612,7 +696,7 @@ 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
 }
 
@@ -629,7 +713,7 @@ 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
 }
 
@@ -646,10 +730,24 @@ 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
 	}