Function refJoin

core/git.go:585–636

refJoin creates a temporary git repository, adds the given refs as remotes, fetches them, and returns a GitCLI instance.

(ctx context.Context, refs []*GitRef)

// refJoin creates a temporary git repository, adds the given refs as remotes,
// fetches them, and returns a GitCLI instance.
func refJoin(ctx context.Context, refs []*GitRef) (_ *gitutil.GitCLI, _ []string, _ func() error, rerr error) {
	tmpDir, err := os.MkdirTemp("", "dagger-mergebase")
	if err != nil {
		return nil, nil, nil, fmt.Errorf("failed to create temp dir: %w", err)
	}
	cleanup := func() error {
		return os.RemoveAll(tmpDir)
	}
	defer func() {
		if rerr != nil {
			cleanup()
		}
	}()
	git := gitutil.NewGitCLI(
		gitutil.WithDir(tmpDir),
		gitutil.WithGitDir(filepath.Join(tmpDir, ".git")),
	)
	if _, err := git.Run(ctx, "-c", "init.defaultBranch=main", "init"); err != nil {
		return nil, nil, nil, fmt.Errorf("failed to init temp repo: %w", err)
	}

	eg, egCtx := errgroup.WithContext(ctx)
	mu := sync.Mutex{} // cannot simultaneously add+fetch remotes
	commits := make([]string, len(refs))

	for i, ref := range refs {
		eg.Go(func() error {
			commits[i] = ref.Ref.SHA
			return ref.Backend.mount(egCtx, 0, false, func(gitN *gitutil.GitCLI) error {
				remoteURL, err := gitN.URL(egCtx)
				if err != nil {
					return err
				}
				remoteName := fmt.Sprintf("origin%d", i+1)
				mu.Lock()
				defer mu.Unlock()
				if _, err := git.Run(egCtx, "remote", "add", remoteName, remoteURL); err != nil {
					return fmt.Errorf("failed to add remote %s: %w", remoteName, err)
				}
				if _, err := git.Run(egCtx, "fetch", "--no-tags", remoteName, ref.Ref.SHA); err != nil {
					return fmt.Errorf("failed to fetch ref %d: %w", i+1, err)
				}
				return nil
			})
		})
	}

	if err := eg.Wait(); err != nil {
		return nil, nil, nil, err
	}
	return git, commits, cleanup, nil
}