failed to create commit: current tip is not the first parent error during commit in libgit2 - libgit2

Question

I am using libgit2 v0.23.0 library for git pull & commit operation. I am calling git_merge(repo,their_heads,1,&merge_opt,&checkout_opts); method & it works fine & merge the changes from remote repository to local repository. But after that when I am calling git_commit_create() method, it throw error as failed to create commit: current tip is not the first parent with error code -15.
I investigate & found that FETCH_HEAD and MERGE_HEAD file contains updated oid, but ORIG_HEAD still containing previous/outdated oid. I am not sure this is the cause of error which I am getting during git_commit_create().
int fetch()
{
qDebug()<<"Fetch";
git_remote *remote = NULL;
const git_transfer_progress *stats;
struct dl_data data;
git_fetch_options fetch_opts = GIT_FETCH_OPTIONS_INIT;
git_repository *repo = NULL;
QString repoPath = "repopath/.git";
int error = git_repository_open(&repo, repoPath.toStdString().c_str());
if (git_remote_lookup(&remote, repo, "origin") < 0) {
if (git_remote_create_anonymous(&remote, repo,"repoURL") < 0)
return -1;
}
fetch_opts.callbacks.update_tips = &update_cb;
fetch_opts.callbacks.sideband_progress = &progress_cb;
fetch_opts.callbacks.credentials = cred_acquire_cb;
data.remote = remote;
data.fetch_opts = &fetch_opts;
data.ret = 0;
data.finished = 0;
stats = git_remote_stats(remote);
download(&data);
if (stats->local_objects > 0) {
printf("\rReceived %d/%d objects in % bytes (used %d local objects)\n",
stats->indexed_objects, stats->total_objects, stats->received_bytes, stats->local_objects);
} else{
printf("\rReceived %d/%d objects in %bytes\n",
stats->indexed_objects, stats->total_objects, stats->received_bytes);
}
git_remote_disconnect(remote);
if (git_remote_update_tips(remote, &fetch_opts.callbacks, 1, fetch_opts.download_tags, NULL) < 0)
return -1;
const git_remote_head **head = NULL;
size_t size = 0;
(git_remote_ls(&head, &size, remote));
git_oid oid = head[0]->oid;
char * commit_id1 = new char[41]; //Commit ID
qDebug()<<"oid:"<<git_oid_tostr(commit_id1, 41, &oid);
git_annotated_commit *anno_out ;
git_annotated_commit_lookup(&anno_out,repo,&oid);
git_checkout_options checkout_opts = GIT_CHECKOUT_OPTIONS_INIT;
checkout_opts.checkout_strategy = GIT_CHECKOUT_FORCE;
const git_annotated_commit **their_heads = const_cast<const git_annotated_commit**>(&anno_out);
git_merge_options merge_opt = GIT_MERGE_OPTIONS_INIT;
merge_opt.file_favor = GIT_MERGE_FILE_FAVOR_UNION;
error = git_merge(repo,their_heads,1,&merge_opt,&checkout_opts);
if(error!=0){
//Error handling
}
else{
qDebug()<<"Merge successfully";
}
git_repository_state_cleanup(repo);
/* Create signature */
git_signature *me = NULL;
(git_signature_now(&me, "username", "username#gmail.com"));
//Tree Lookup
git_tree *tree;
git_object *tree_obj;
(git_revparse_single(&tree_obj, repo, "HEAD^{tree}"));
// Get parent commit
git_oid parentCommitId;
git_commit *parent;
git_oid remoteParentCommitId;
git_commit *remoteParent;
int nparents;
int err;
(git_reference_name_to_id( &parentCommitId, repo, "ORIG_HEAD" ));
(git_commit_lookup( &parent, repo, &parentCommitId ));
(git_reference_name_to_id( &remoteParentCommitId, repo, "MERGE_HEAD" ));
(git_commit_lookup( &remoteParent, repo, &remoteParentCommitId ));
const git_commit *parents [1] = {remoteParent };
git_oid new_commit_id;
err = (git_commit_create(
&new_commit_id,
repo,
"HEAD", /* name of ref to update */
me, /* author */
me, /* committer */
"UTF-8", /* message encoding */
"pull fetch", /* message */
(git_tree *) tree_obj, /* root tree */
1, /* parent count */
parents)); /* parents */
if(err !=0){
//I am getting error here
}
git_remote_free(remote);
return 0;
}
Please suggest me what I have to do in order to resolve this issue ?

Answer 1

Generally, you're seeing this error because you are building a new commit on a branch whose parent is not the current tip of the branch. Indeed, you're building a new commit whose parent is the remote commit not the local one.
There are a few problems:
Some error checking on all the functions is recommended. I see some functions that are likely failing but there is no check for that. For example:
Don't call git_repository_state_cleanup in the middle of your operation. That will abort the merge and cleanup the state files that you're trying to read later. Like MERGE_HEAD.
You're doing a merge. You should have two parent commits (the two commits you're merging) to the new commit. You should pass { parent, remoteParent } as the parents.