1 files changed, 152 insertions, 0 deletions
diff --git a/storage/seekable/internal/gitdir/refs.go b/storage/seekable/internal/gitdir/refs.go
new file mode 100644
index 0000000..9c2e8fb
--- /dev/null
+++ b/storage/seekable/internal/gitdir/refs.go
@@ -0,0 +1,152 @@
+package gitdir
+
+import (
+	"bufio"
+	"errors"
+	"io/ioutil"
+	"os"
+	"strings"
+
+	"gopkg.in/src-d/go-git.v3/core"
+)
+
+var (
+	// ErrPackedRefsDuplicatedRef is returned when a duplicated
+	// reference is found in the packed-ref file. This is usually the
+	// case for corrupted git repositories.
+	ErrPackedRefsDuplicatedRef = errors.New("duplicated ref found in packed-ref file")
+	// ErrPackedRefsBadFormat is returned when the packed-ref file
+	// corrupt.
+	ErrPackedRefsBadFormat = errors.New("malformed packed-ref")
+	// ErrSymRefTargetNotFound is returned when a symbolic reference is
+	// targeting a non-existing object. This usually means the
+	// repository is corrupt.
+	ErrSymRefTargetNotFound = errors.New("symbolic reference target not found")
+)
+
+const (
+	symRefPrefix = "ref: "
+)
+
+func (d *GitDir) addRefsFromPackedRefs() (err error) {
+	path := d.fs.Join(d.path, packedRefsPath)
+	f, err := d.fs.Open(path)
+	if err != nil {
+		if err == os.ErrNotExist {
+			return nil
+		}
+		return err
+	}
+	defer func() {
+		errClose := f.Close()
+		if err == nil {
+			err = errClose
+		}
+	}()
+
+	s := bufio.NewScanner(f)
+	for s.Scan() {
+		line := s.Text()
+		if err = d.processLine(line); err != nil {
+			return err
+		}
+	}
+
+	return s.Err()
+}
+
+// process lines from a packed-refs file
+func (d *GitDir) processLine(line string) error {
+	switch line[0] {
+	case '#': // comment - ignore
+		return nil
+	case '^': // annotated tag commit of the previous line - ignore
+		return nil
+	default:
+		ws := strings.Split(line, " ") // hash then ref
+		if len(ws) != 2 {
+			return ErrPackedRefsBadFormat
+		}
+		h, r := ws[0], ws[1]
+
+		if _, ok := d.refs[r]; ok {
+			return ErrPackedRefsDuplicatedRef
+		}
+		d.refs[r] = core.NewHash(h)
+	}
+
+	return nil
+}
+
+func (d *GitDir) addRefsFromRefDir() error {
+	return d.walkTree("refs")
+}
+
+func (d *GitDir) walkTree(relPath string) error {
+	files, err := d.fs.ReadDir(d.fs.Join(d.path, relPath))
+	if err != nil {
+		return err
+	}
+
+	for _, f := range files {
+		newRelPath := d.fs.Join(relPath, f.Name())
+
+		if f.IsDir() {
+			if err = d.walkTree(newRelPath); err != nil {
+				return err
+			}
+		} else {
+			filePath := d.fs.Join(d.path, newRelPath)
+			h, err := d.readHashFile(filePath)
+			if err != nil {
+				return err
+			}
+			d.refs[newRelPath] = h
+		}
+	}
+
+	return nil
+}
+
+// ReadHashFile reads a single hash from a file.  If a symbolic
+// reference is found instead of a hash, the reference is resolved and
+// the proper hash is returned.
+func (d *GitDir) readHashFile(path string) (h core.Hash, err error) {
+	f, err := d.fs.Open(path)
+	if err != nil {
+		return core.ZeroHash, err
+	}
+	defer func() {
+		errClose := f.Close()
+		if err == nil {
+			err = errClose
+		}
+	}()
+
+	b, err := ioutil.ReadAll(f)
+	if err != nil {
+		return core.ZeroHash, err
+	}
+	line := strings.TrimSpace(string(b))
+
+	if isSymRef(line) {
+		return d.resolveSymRef(line)
+	}
+
+	return core.NewHash(line), nil
+}
+
+func isSymRef(contents string) bool {
+	return strings.HasPrefix(contents, symRefPrefix)
+}
+
+func (d *GitDir) resolveSymRef(symRef string) (core.Hash, error) {
+	ref := strings.TrimPrefix(symRef, symRefPrefix)
+
+	hash, ok := d.refs[ref]
+	if !ok {
+		return core.ZeroHash, ErrSymRefTargetNotFound
+	}
+
+	return hash, nil
+}