First pass of prune design

1 files changed, 124 insertions, 0 deletions

diff --git a/repository.go b/repository.go
index b159ff0..7079fd1 100644
--- a/repository.go
+++ b/repository.go
@@ -8,10 +8,12 @@ import (
 	"os"
 	"path/filepath"
 	"strings"
+	"time"
 
 	"gopkg.in/src-d/go-git.v4/config"
 	"gopkg.in/src-d/go-git.v4/internal/revision"
 	"gopkg.in/src-d/go-git.v4/plumbing"
+	"gopkg.in/src-d/go-git.v4/plumbing/filemode"
 	"gopkg.in/src-d/go-git.v4/plumbing/object"
 	"gopkg.in/src-d/go-git.v4/plumbing/storer"
 	"gopkg.in/src-d/go-git.v4/storage"
@@ -1011,3 +1013,125 @@ func (r *Repository) ResolveRevision(rev plumbing.Revision) (*plumbing.Hash, err
 
 	return &commit.Hash, nil
 }
+
+type PruneHandler func(unreferencedObjectHash plumbing.Hash) error
+type PruneOptions struct {
+	// OnlyObjectsOlderThan if set to non-zero value
+	// selects only objects older than the time provided.
+	OnlyObjectsOlderThan time.Time
+	// Handler is called on matching objects
+	Handler PruneHandler
+}
+
+// DeleteObject deletes an object from a repository.
+// The type conveniently matches PruneHandler.
+func (r *Repository) DeleteObject(hash plumbing.Hash) error {
+	return r.Storer.DeleteLooseObject(hash)
+}
+
+func (r *Repository) Prune(opt PruneOptions) error {
+	pw := &pruneWalker{
+		r:    r,
+		seen: map[plumbing.Hash]struct{}{},
+	}
+	// Walk over all the references in the repo.
+	it, err := r.Storer.IterReferences()
+	if err != nil {
+		return nil
+	}
+	defer it.Close()
+	err = it.ForEach(func(ref *plumbing.Reference) error {
+		// Exit this iteration early for non-hash references.
+		if ref.Type() != plumbing.HashReference {
+			return nil
+		}
+		return pw.walkObjectTree(ref.Hash())
+	})
+	if err != nil {
+		return err
+	}
+	// Now walk all (loose) objects in storage.
+	err = r.Storer.ForEachObjectHash(func(hash plumbing.Hash) error {
+		// Get out if we have seen this object.
+		if pw.isSeen(hash) {
+			return nil
+		}
+		// Otherwise it is a candidate for pruning.
+		// Check out for too new objects next.
+		if opt.OnlyObjectsOlderThan != (time.Time{}) {
+			// Errors here are non-fatal. The object may be e.g. packed.
+			// Or concurrently deleted. Skip such objects.
+			t, err := r.Storer.LooseObjectTime(hash)
+			if err != nil {
+				return nil
+			}
+			// Skip too new objects.
+			if !t.Before(opt.OnlyObjectsOlderThan) {
+				return nil
+			}
+		}
+		return opt.Handler(hash)
+	})
+	if err != nil {
+		return err
+	}
+	return nil
+}
+
+type pruneWalker struct {
+	r    *Repository
+	seen map[plumbing.Hash]struct{}
+}
+
+func (p *pruneWalker) isSeen(hash plumbing.Hash) bool {
+	_, seen := p.seen[hash]
+	return seen
+}
+
+func (p *pruneWalker) add(hash plumbing.Hash) {
+	p.seen[hash] = struct{}{}
+}
+
+func (p *pruneWalker) walkObjectTree(hash plumbing.Hash) error {
+	// Check if we have already seen, and mark this object
+	if p.isSeen(hash) {
+		return nil
+	}
+	p.add(hash)
+	// Fetch the object.
+	obj, err := object.GetObject(p.r.Storer, hash)
+	if err != nil {
+		return fmt.Errorf("Getting object %s failed: %v", hash, err)
+	}
+	// Walk all children depending on object type.
+	switch obj := obj.(type) {
+	case *object.Commit:
+		err = p.walkObjectTree(obj.TreeHash)
+		if err != nil {
+			return err
+		}
+		for _, h := range obj.ParentHashes {
+			err = p.walkObjectTree(h)
+			if err != nil {
+				return err
+			}
+		}
+	case *object.Tree:
+		for i := range obj.Entries {
+			// Shortcut for blob objects:
+			if obj.Entries[i].Mode|0755 == filemode.Executable {
+				p.add(obj.Entries[i].Hash)
+				continue
+			}
+			// Normal walk for sub-trees (and symlinks etc).
+			err = p.walkObjectTree(obj.Entries[i].Hash)
+			if err != nil {
+				return err
+			}
+		}
+	default:
+		// Error out on unhandled object types.
+		return fmt.Errorf("Unknown object %X %s %T\n", obj.ID(), obj.Type(), obj)
+	}
+	return nil
+}