Question

How to clone a repo (with libgit2)

I want to do exactly what git clone does but with libgit2. What I may be asking is what git clone really does in depth.

This is what I’m doing so far:

1. Initialize a repo
2. Adjust the config file to add the remote
3. Create a git_remote
4. Download a packfile
5. Index the packfile and write the index (gives us a .idx file)
6. (edit) Write all the different branches to disk.
7. (edit) Do git checkout in some way.

And now I have no idea what to do. My only guess would be to load the .idx to a git_index and use git_repository_set_index, but that didn’t show any files either.

Edit

I tested running git checkout master on the half-cloned repo, and that did the job. Now I just need to find out how to do it with libgit2, and it seems like there is some useful information in the issue tracker.

Edit 2

I will now add my current code, in hope that someone someday will find it useful, in hope to be that quick-start code I never found. Note: I’m using Obj-C and Objective-Git here, but it’s mainly plain c.

+ (GTRepository *)cloneFromRemoteURL:(NSURL *)remoteURL toLocalURL:(NSURL *)localURL
{   
// Let's suppose the URL looks like: https://github.com/libgit2/libgit2.git
// Then we need to get a URL like this too: git://github.com/libgit2/libgit2.git
// This may be a bit dodgy, but it will do for now.
const char *gitURL = [remoteURL.absoluteString stringByReplacingOccurrencesOfString:@"https://github.com/" withString:@"git://github.com/"].UTF8String;

//Setup
int error;
git_repository *repo
git_config *cfg;
git_remote *remote;

NSURL *gitDirURL = [localURL URLByAppendingPathComponent:@".git"];

error = git_repository_open(&repo, gitDirURL.path.UTF8String);
    if (error != GIT_SUCCESS) {

    git_repository_init(&repo, gitDirURL.path.UTF8String, 1);

    //Config
    git_repository_config(&cfg, repo);
    git_config_set_int32 (cfg, "core.repositoryformatversion", 0);
    git_config_set_bool (cfg, "core.filemode", 1);
    git_config_set_bool (cfg, "core.bare", 0);
    git_config_set_bool (cfg, "core.logallrefupdates", 1);
    git_config_set_bool (cfg, "core.ignorecase", 1);
    git_config_set_string (cfg, "remote.origin.url", gitURL);
    git_config_set_string (cfg, "remote.origin.fetch", "+refs/heads/*:refs/remotes/origin/*");
    git_config_set_string (cfg, "branch.master.remote", "origin");
    git_config_set_string (cfg, "branch.master.merge", "refs/heads/master");

    git_repository_set_workdir(repo, localURL.path.UTF8String);

    error = git_remote_new(&remote, repo, "A remote", gitURL, "origin");

    git_repository_free(repo);
    git_repository_open (&repo, localURL.path.UTF8String);
}



git_repository_config(&cfg, repo);

// connect to repo
error = git_remote_load(&remote, repo, "origin");

error = git_remote_connect(remote, GIT_DIR_FETCH);
// get pack file

git_off_t bytes;
git_indexer_stats stats;
error = git_remote_download(remote, &bytes, &stats);

NSURL *packFolderURL = [localURL URLByAppendingPathComponent:@".git/objects/pack"];
NSFileManager *fileManager = [NSFileManager defaultManager];
NSArray *array = [fileManager contentsOfDirectoryAtURL:packFolderURL includingPropertiesForKeys:nil options:0 error:nil];
NSLog(@"Dictionary:%@",array);
NSString *result;
for (NSURL *url in array) {
    if ([url.path rangeOfString:@".pack"].location != NSNotFound) {
        result = url.path;
    }
}
const char *packname = [result UTF8String];


// unpack pack file
if (packname != NULL) 
{
    git_indexer *indexer;
    git_indexer_stats stats2;
    int error;
    char hash[GIT_OID_HEXSZ + 1] = {0};

    error = git_indexer_new(&indexer, packname);
    error = git_indexer_run(indexer, &stats2);
    error = git_indexer_write(indexer);

    // Get the packfile's hash (which should become it's filename)
    git_oid_fmt(hash, git_indexer_hash(indexer));

    NSString *hashStr = [NSString stringWithCString:hash encoding:NSUTF8StringEncoding];
    hashStr = [NSString stringWithFormat:@"pack-%@.idx",hashStr];
    const char *indexPath = [hashStr UTF8String];

    puts(hash);
    git_index *index;
    git_index_open(&index, indexPath);
    git_index_read(index);
    git_repository_set_index(repo, index);


    git_indexer_free(indexer);
    git_remote_update_tips(remote, update_cb2); //No idea what it does, but it seems like it's important… It does make the branches appear in .git/refs/remotes/origin

}

//Somehow do git checkout master here

return [GTRepository repositoryWithURL:localURL error:nil];

}

Answer 1

Since the libgit2 doesn’t explicitly mention git clone in its issue list, one lead to follow is in the sources of the original git project with:

• builtin/clone.c
• contrib/examples/git-clone.sh

That last script will guide you through all the stages of a git clone.