knotserver: add generic git repo walker interface

Signed-off-by: oppiliappan <[e-mail]>

knotserver/git/tree.go

···
 
 import (
 	"context"
+	"errors"
 	"fmt"
 	"path"
 	"time"
···
 
 	return nts
 }
+
+var (
+	TerminateWalk error = errors.New("terminate walk")
+)
+
+type callback = func(node object.TreeEntry, parent *object.Tree, fullPath string) error
+
+func (g *GitRepo) Walk(
+	ctx context.Context,
+	root string,
+	cb callback,
+) error {
+	c, err := g.r.CommitObject(g.h)
+	if err != nil {
+		return fmt.Errorf("commit object: %w", err)
+	}
+
+	tree, err := c.Tree()
+	if err != nil {
+		return fmt.Errorf("file tree: %w", err)
+	}
+
+	subtree := tree
+	if root != "" {
+		subtree, err = tree.Tree(root)
+		if err != nil {
+			return fmt.Errorf("sub tree: %w", err)
+		}
+	}
+
+	return g.walkHelper(ctx, root, subtree, cb)
+}
+
+func (g *GitRepo) walkHelper(
+	ctx context.Context,
+	root string,
+	currentTree *object.Tree,
+	cb callback,
+) error {
+	for _, e := range currentTree.Entries {
+		// check if context hits deadline before processing
+		select {
+		case <-ctx.Done():
+			return ctx.Err()
+		default:
+		}
+
+		mode, err := e.Mode.ToOSFileMode()
+		if err != nil {
+			// TODO: log this
+			continue
+		}
+
+		if e.Mode.IsFile() {
+			err = cb(e, currentTree, root)
+			if errors.Is(err, TerminateWalk) {
+				return err
+			}
+		}
+
+		// e is a directory
+		if mode.IsDir() {
+			subtree, err := currentTree.Tree(e.Name)
+			if err != nil {
+				return fmt.Errorf("sub tree %s: %w", e.Name, err)
+			}
+
+			fullPath := path.Join(root, e.Name)
+
+			err = g.walkHelper(ctx, fullPath, subtree, cb)
+			if err != nil {
+				return err
+			}
+		}
+	}
+
+	return nil
+}