rebase: Add wrapper for `git_rebase_inmemory_index()` (#900)

* rebase: Fix missing initialization of the repo pointer

While the `Rebase` structure has a pointer to the repository the rebase
is creatde in, this pointer isn't ever initialized. Fix this.

* rebase: Add wrapper for `git_rebase_inmemory_index()`

Add a new wrapper for `git_rebase_inmemory_index()`, which can be used
to retrieve the index for an in-memory rebase.

Co-authored-by: Patrick Steinhardt <[email protected]>

1 files changed, 25 insertions, 4 deletions

diff --git a/rebase.go b/rebase.go
index 58c0b6f..b9c94fd 100644
--- a/rebase.go
+++ b/rebase.go
@@ -318,7 +318,7 @@ func (r *Repository) InitRebase(branch *AnnotatedCommit, upstream *AnnotatedComm
 		return nil, MakeGitError(ret)
 	}
 
-	return newRebaseFromC(ptr, cOpts), nil
+	return newRebaseFromC(ptr, r, cOpts), nil
 }
 
 // OpenRebase opens an existing rebase that was previously started by either an invocation of InitRebase or by another client.
@@ -340,7 +340,7 @@ func (r *Repository) OpenRebase(opts *RebaseOptions) (*Rebase, error) {
 		return nil, MakeGitError(ret)
 	}
 
-	return newRebaseFromC(ptr, cOpts), nil
+	return newRebaseFromC(ptr, r, cOpts), nil
 }
 
 // OperationAt gets the rebase operation specified by the given index.
@@ -392,6 +392,27 @@ func (rebase *Rebase) Next() (*RebaseOperation, error) {
 	return newRebaseOperationFromC(ptr), nil
 }
 
+// InmemoryIndex gets the index produced by the last operation, which is the
+// result of `Next()` and which will be committed by the next invocation of
+// `Commit()`. This is useful for resolving conflicts in an in-memory rebase
+// before committing them.
+//
+// This is only applicable for in-memory rebases; for rebases within a working
+// directory, the changes were applied to the repository's index.
+func (rebase *Rebase) InmemoryIndex() (*Index, error) {
+	runtime.LockOSThread()
+	defer runtime.UnlockOSThread()
+
+	var ptr *C.git_index
+	err := C.git_rebase_inmemory_index(&ptr, rebase.ptr)
+	runtime.KeepAlive(rebase)
+	if err < 0 {
+		return nil, MakeGitError(err)
+	}
+
+	return newIndexFromC(ptr, rebase.r), nil
+}
+
 // Commit commits the current patch.
 // You must have resolved any conflicts that were introduced during the patch application from the Next() invocation.
 func (rebase *Rebase) Commit(ID *Oid, author, committer *Signature, message string) error {
@@ -457,8 +478,8 @@ func (r *Rebase) Free() {
 	freeRebaseOptions(r.options)
 }
 
-func newRebaseFromC(ptr *C.git_rebase, opts *C.git_rebase_options) *Rebase {
-	rebase := &Rebase{ptr: ptr, options: opts}
+func newRebaseFromC(ptr *C.git_rebase, repo *Repository, opts *C.git_rebase_options) *Rebase {
+    rebase := &Rebase{ptr: ptr, r: repo, options: opts}
 	runtime.SetFinalizer(rebase, (*Rebase).Free)
 	return rebase
 }