1 files changed, 174 insertions, 0 deletions
diff --git a/submodule.go b/submodule.go
new file mode 100644
index 0000000..e329fda
--- /dev/null
+++ b/submodule.go
@@ -0,0 +1,174 @@
+package git
+
+import (
+	"errors"
+
+	"srcd.works/go-git.v4/config"
+	"srcd.works/go-git.v4/plumbing"
+)
+
+var (
+	ErrSubmoduleAlreadyInitialized = errors.New("submodule already initialized")
+	ErrSubmoduleNotInitialized     = errors.New("submodule not initialized")
+)
+
+// Submodule a submodule allows you to keep another Git repository in a
+// subdirectory of your repository.
+type Submodule struct {
+	initialized bool
+
+	c *config.Submodule
+	w *Worktree
+}
+
+// Config returns the submodule config
+func (s *Submodule) Config() *config.Submodule {
+	return s.c
+}
+
+// Init initialize the submodule reading the recoreded Entry in the index for
+// the given submodule
+func (s *Submodule) Init() error {
+	cfg, err := s.w.r.Storer.Config()
+	if err != nil {
+		return err
+	}
+
+	_, ok := cfg.Submodules[s.c.Name]
+	if ok {
+		return ErrSubmoduleAlreadyInitialized
+	}
+
+	s.initialized = true
+
+	cfg.Submodules[s.c.Name] = s.c
+	return s.w.r.Storer.SetConfig(cfg)
+}
+
+// Repository returns the Repository represented by this submodule
+func (s *Submodule) Repository() (*Repository, error) {
+	storer, err := s.w.r.Storer.Module(s.c.Name)
+	if err != nil {
+		return nil, err
+	}
+
+	_, err = storer.Reference(plumbing.HEAD)
+	if err != nil && err != plumbing.ErrReferenceNotFound {
+		return nil, err
+	}
+
+	worktree := s.w.fs.Dir(s.c.Path)
+	if err == nil {
+		return Open(storer, worktree)
+	}
+
+	r, err := Init(storer, worktree)
+	if err != nil {
+		return nil, err
+	}
+
+	_, err = r.CreateRemote(&config.RemoteConfig{
+		Name: DefaultRemoteName,
+		URL:  s.c.URL,
+	})
+
+	return r, err
+}
+
+// Update the registered submodule to match what the superproject expects, the
+// submodule should be initilized first calling the Init method or setting in
+// the options SubmoduleUpdateOptions.Init equals true
+func (s *Submodule) Update(o *SubmoduleUpdateOptions) error {
+	if !s.initialized && !o.Init {
+		return ErrSubmoduleNotInitialized
+	}
+
+	if !s.initialized && o.Init {
+		if err := s.Init(); err != nil {
+			return err
+		}
+	}
+
+	e, err := s.w.readIndexEntry(s.c.Path)
+	if err != nil {
+		return err
+	}
+
+	r, err := s.Repository()
+	if err != nil {
+		return err
+	}
+
+	if err := s.fetchAndCheckout(r, o, e.Hash); err != nil {
+		return err
+	}
+
+	return s.doRecrusiveUpdate(r, o)
+}
+
+func (s *Submodule) doRecrusiveUpdate(r *Repository, o *SubmoduleUpdateOptions) error {
+	if o.RecurseSubmodules == NoRecurseSubmodules {
+		return nil
+	}
+
+	w, err := r.Worktree()
+	if err != nil {
+		return err
+	}
+
+	l, err := w.Submodules()
+	if err != nil {
+		return err
+	}
+
+	new := &SubmoduleUpdateOptions{}
+	*new = *o
+	new.RecurseSubmodules--
+	return l.Update(new)
+}
+
+func (s *Submodule) fetchAndCheckout(r *Repository, o *SubmoduleUpdateOptions, hash plumbing.Hash) error {
+	if !o.NoFetch {
+		err := r.Fetch(&FetchOptions{})
+		if err != nil && err != NoErrAlreadyUpToDate {
+			return err
+		}
+	}
+
+	w, err := r.Worktree()
+	if err != nil {
+		return err
+	}
+
+	if err := w.Checkout(hash); err != nil {
+		return err
+	}
+
+	head := plumbing.NewHashReference(plumbing.HEAD, hash)
+	return r.Storer.SetReference(head)
+}
+
+// Submodules list of several submodules from the same repository
+type Submodules []*Submodule
+
+// Init initializes the submodules in this list
+func (s Submodules) Init() error {
+	for _, sub := range s {
+		if err := sub.Init(); err != nil {
+			return err
+		}
+	}
+
+	return nil
+}
+
+// Update updates all the submodules in this list
+func (s Submodules) Update(o *SubmoduleUpdateOptions) error {
+	for _, sub := range s {
+		if err := sub.Update(o); err != nil {
+			return err
+		}
+	}
+
+	return nil
+}