how to use libgit2 to fetch from the git? - libgit2

Question

I read the fetch.c and try to update the content in local repository(just like "git fetch"), but git_remote_connect return -1.
err:Unexpected HTTP status code: 401
where to set the cred when connect to the remote? What is wrong with the code?? Thx.
(IBAction)Fetch:(id)sender {
git_remote *remote = NULL;
const git_error *err = NULL;
int ret = -1;
bool invoked = false;
git_repository *repo = NULL;
NSArray *str = NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES);
NSString *docPath = [str objectAtIndex:0];
NSString *localPath = [docPath stringByAppendingPathComponent:#"abc/.git"];
NSLog(#"localPath:%#", localPath);
ret = git_repository_open(&repo, [localPath UTF8String]);
NSLog(#"git_repository_open ret:%d",ret);
err = giterr_last();
if(err == NULL)
{
NSLog(#"NULL");
}
else
{
NSLog(#"err:%s", err->message);
}
ret = git_remote_load(&remote, repo, "origin");
NSLog(#"git_remote_load ret:%d", ret);
err = giterr_last();
if(err == NULL)
{
NSLog(#"No error");
}
else
{
NSLog(#"err:%s", err->message);
return;
}
ret = git_remote_load(&remote, repo, "origin");
NSLog(#"git_remote_load ret:%d", ret);
ret = git_remote_connect(remote, GIT_DIRECTION_FETCH);
NSLog(#"git_remote_connect ret:%d", ret);
err = giterr_last();
if(err == NULL)
{
NSLog(#"No error");
}
else
{
NSLog(#"err:%s", err->message);
return;
}
ret = git_remote_download(remote, &transferProgressCallback, &invoked);
NSLog(#"git_remote_download ret:%d", ret);
err = giterr_last();
if(err == NULL)
{
NSLog(#"No error");
}
else
{
NSLog(#"err:%s", err->message);
return;
}
ret = git_remote_update_tips(remote);
NSLog(#"git_remote_update_tips ret:%d", ret);
err = giterr_last();
if(err == NULL)
{
NSLog(#"No error");
}
else
{
NSLog(#"err:%s", err->message);
return;
}
}
here is the remote config
[remote "origin"]
url = http://remote_path/git/share.git
fetch = +refs/heads/*:refs/remotes/origin/*
[branch "master"]
remote = origin
merge = refs/heads/master

Answer 1

I find the function below to set cred which the remote acquire
bool invoked = false;
git_remote_set_cred_acquire_cb(remote, cred_acquire_cb, &invoked);
The code of cred_acquire_cb is below:
static int cred_acquire_cb(git_cred **cred, const char *url, unsigned int allowed_types, void *payload)
{
char *_remote_user = "user";
char *_remote_pass = "pass";
*((bool*)payload) = true;
if ((GIT_CREDTYPE_USERPASS_PLAINTEXT & allowed_types) == 0 ||
git_cred_userpass_plaintext_new(cred, _remote_user, _remote_pass) < 0)
return -1;
return 0;
}