commit: add keep-alives for those that need conversion to pointer receivers

We can't work on the copies here, we need to have pointer receivers so we know
we're keeping alive the object whose finalizer would free the unmanaged memory
we're working with.

Author: carlosmn

commit.go

@@ -18,15 +18,19 @@ type Commit struct {
 	cast_ptr *C.git_commit
 }
 
-func (c Commit) Message() string {
-	return C.GoString(C.git_commit_message(c.cast_ptr))
+func (c *Commit) Message() string {
+	ret := C.GoString(C.git_commit_message(c.cast_ptr))
+	runtime.KeepAlive(c)
+	return ret
 }
 
-func (c Commit) RawMessage() string {
-	return C.GoString(C.git_commit_message_raw(c.cast_ptr))
+func (c *Commit) RawMessage() string {
+	ret := C.GoString(C.git_commit_message_raw(c.cast_ptr))
+	runtime.KeepAlive(c)
+	return ret
 }
 
-func (c Commit) ExtractSignature() (string, string, error) {
+func (c *Commit) ExtractSignature() (string, string, error) {
 
 	var c_signed C.git_buf
 	defer C.git_buf_free(&c_signed)
@@ -40,7 +44,7 @@ func (c Commit) ExtractSignature() (string, string, error) {
 	runtime.LockOSThread()
 	defer runtime.UnlockOSThread()
 	ret := C.git_commit_extract_signature(&c_signature, &c_signed, repo, oid.toC(), nil)
-
+	runtime.KeepAlive(oid)
 	if ret < 0 {
 		return "", "", MakeGitError(ret)
 	} else {
@@ -49,36 +53,45 @@ func (c Commit) ExtractSignature() (string, string, error) {
 
 }
 
-func (c Commit) Summary() string {
-	return C.GoString(C.git_commit_summary(c.cast_ptr))
+func (c *Commit) Summary() string {
+	ret := C.GoString(C.git_commit_summary(c.cast_ptr))
+	runtime.KeepAlive(c)
+	return ret
 }
 
-func (c Commit) Tree() (*Tree, error) {
+func (c *Commit) Tree() (*Tree, error) {
 	var ptr *C.git_tree
 
 	runtime.LockOSThread()
 	defer runtime.UnlockOSThread()
 
 	err := C.git_commit_tree(&ptr, c.cast_ptr)
+	runtime.KeepAlive(c)
 	if err < 0 {
 		return nil, MakeGitError(err)
 	}
 
 	return allocTree(ptr, c.repo), nil
 }
 
-func (c Commit) TreeId() *Oid {
-	return newOidFromC(C.git_commit_tree_id(c.cast_ptr))
+func (c *Commit) TreeId() *Oid {
+	ret := newOidFromC(C.git_commit_tree_id(c.cast_ptr))
+	runtime.KeepAlive(c)
+	return c
 }
 
-func (c Commit) Author() *Signature {
+func (c *Commit) Author() *Signature {
 	cast_ptr := C.git_commit_author(c.cast_ptr)
-	return newSignatureFromC(cast_ptr)
+	ret := newSignatureFromC(cast_ptr)
+	runtime.KeepAlive(c)
+	return ret
 }
 
-func (c Commit) Committer() *Signature {
+func (c *Commit) Committer() *Signature {
 	cast_ptr := C.git_commit_committer(c.cast_ptr)
-	return newSignatureFromC(cast_ptr)
+	ret := newSignatureFromC(cast_ptr)
+	runtime.KeepAlive(c)
+	return ret
 }
 
 func (c *Commit) Parent(n uint) *Commit {