feat: Introduce .kraftignore

Signed-off-by: Md Sahil <mohdssahil1@gmail.com>

initrd/directory.go

@@ -65,6 +65,12 @@ func (initrd *directory) Build(ctx context.Context) (string, error) {
 		}
 	}
 
+	if _, err := os.Stat(initrd.opts.output); err == nil {
+		if err = os.Remove(initrd.opts.output); err != nil {
+			return "", err
+		}
+	}
+
 	f, err := os.OpenFile(initrd.opts.output, os.O_RDWR|os.O_CREATE, 0o644)
 	if err != nil {
 		return "", fmt.Errorf("could not open initramfs file: %w", err)
@@ -75,6 +81,11 @@ func (initrd *directory) Build(ctx context.Context) (string, error) {
 	writer := cpio.NewWriter(f)
 	defer writer.Close()
 
+	ignoringItems, err := getKraftignoreItems(ctx, initrd)
+	if err != nil {
+		return "", err
+	}
+
 	if err := filepath.WalkDir(initrd.path, func(path string, d fs.DirEntry, err error) error {
 		if err != nil {
 			return fmt.Errorf("received error before parsing path: %w", err)
@@ -86,6 +97,21 @@ func (initrd *directory) Build(ctx context.Context) (string, error) {
 		}
 		internal = "." + filepath.ToSlash(internal)
 
+		if len(ignoringItems) > 0 && path != initrd.path {
+			switch isExistInKraftignoreFile(internal, d, ignoringItems) {
+			case SkipDir:
+				log.G(ctx).
+					WithField("directory", internal).
+					Trace("ignoring from archiving")
+				return filepath.SkipDir
+			case Exist:
+				log.G(ctx).
+					WithField("file", internal).
+					Trace("ignoring from archiving")
+				return nil
+			}
+		}
+
 		info, err := d.Info()
 		if err != nil {
 			return fmt.Errorf("could not get directory entry info: %w", err)

initrd/kraftignore.go

@@ -0,0 +1,132 @@
+// SPDX-License-Identifier: BSD-3-Clause
+// Copyright (c) 2022, Unikraft GmbH and The KraftKit Authors.
+// Licensed under the BSD-3-Clause License (the "License").
+// You may not use this file except in compliance with the License.
+package initrd
+
+import (
+	"bufio"
+	"context"
+	"errors"
+	"fmt"
+	"io/fs"
+	"os"
+	"path/filepath"
+	"strings"
+
+	"kraftkit.sh/log"
+)
+
+// kraftignore filename
+const KraftignoreFileName = ".kraftignore"
+
+type IgnoringFileType string
+
+const (
+	Exist    = IgnoringFileType("Exist")
+	NotExist = IgnoringFileType("NotExist")
+	SkipDir  = IgnoringFileType("SkipDir")
+)
+
+func getKraftignoreItems(ctx context.Context, initrd *directory) ([]string, error) {
+	if initrd.opts.kraftignorePath == "" {
+		cwd, err := os.Getwd()
+		if err != nil {
+			return []string{}, err
+		}
+		initrd.opts.kraftignorePath = filepath.Join(cwd, KraftignoreFileName)
+	}
+
+	if _, err := os.Stat(initrd.opts.kraftignorePath); errors.Is(err, os.ErrNotExist) {
+		return []string{}, nil
+	} else if err != nil {
+		return []string{}, err
+	}
+
+	kraftignoreFile, err := os.Open(initrd.opts.kraftignorePath)
+	if err != nil {
+		return []string{}, err
+	}
+
+	defer func() {
+		kraftIgnoreErr := kraftignoreFile.Close()
+		if kraftIgnoreErr != nil {
+			if err != nil {
+				err = fmt.Errorf("%v\n%v", err, kraftIgnoreErr)
+			} else {
+				err = kraftIgnoreErr
+			}
+		}
+	}()
+
+	kraftignoreScanner := bufio.NewScanner(kraftignoreFile)
+	kraftignoreScanner.Split(bufio.ScanLines)
+	var kraftignoreFileLines, ignoringItems []string
+
+	for kraftignoreScanner.Scan() {
+		kraftignoreFileLines = append(kraftignoreFileLines, kraftignoreScanner.Text())
+	}
+
+	for lineNum, line := range kraftignoreFileLines {
+		line = strings.TrimSpace(line)
+		if line == "" || strings.HasPrefix(line, "#") {
+			continue
+		}
+		items := strings.Split(line, " ")
+		for _, item := range items {
+			item = strings.Trim(item, `"`)
+			item = strings.Trim(item, `'`)
+			item = strings.TrimSpace(item)
+			if item == "" || item == "#" {
+				continue
+			}
+
+			if hasGlobPatterns(item) {
+				log.G(ctx).
+					WithField("file", initrd.opts.kraftignorePath).
+					Warn("contains a glob pattern ", item,
+						" at line ", lineNum,
+						" which is not supported by Kraftkit")
+				continue
+			}
+
+			if strings.HasPrefix(item, "..") {
+				item = strings.TrimPrefix(item, "..")
+			}
+
+			item = filepath.Join(item)
+			if !strings.HasPrefix(item, "./") {
+				if !strings.HasPrefix(item, "/") {
+					item = "/" + item
+				}
+				item = "." + item
+			}
+
+			item = strings.TrimSuffix(item, string(filepath.Separator))
+			ignoringItems = append(ignoringItems, item)
+		}
+	}
+
+	return ignoringItems, err
+}
+
+func isExistInKraftignoreFile(internal string, pathInfo fs.DirEntry, kraftignoreItems []string) IgnoringFileType {
+	for _, ignoringItem := range kraftignoreItems {
+		if internal == ignoringItem {
+			if pathInfo.IsDir() {
+				return SkipDir
+			}
+			return Exist
+		}
+	}
+	return NotExist
+}
+
+func hasGlobPatterns(item string) bool {
+	if strings.Contains(item, "*") || strings.Contains(item, "?") ||
+		strings.Contains(item, "!") || strings.Contains(item, "[") ||
+		strings.Contains(item, "{") {
+		return true
+	}
+	return false
+}

initrd/options.go

@@ -4,10 +4,15 @@
 // You may not use this file except in compliance with the License.
 package initrd
 
+import (
+	"path/filepath"
+)
+
 type InitrdOptions struct {
-	output   string
-	cacheDir string
-	arch     string
+	output          string
+	cacheDir        string
+	arch            string
+	kraftignorePath string
 }
 
 type InitrdOption func(*InitrdOptions) error
@@ -41,3 +46,11 @@ func WithArchitecture(arch string) InitrdOption {
 		return nil
 	}
 }
+
+// WithKraftignorePath sets the path for .kraftignore.
+func WithKraftignorePath(dir string) InitrdOption {
+	return func(opts *InitrdOptions) error {
+		opts.kraftignorePath = filepath.Join(dir, KraftignoreFileName)
+		return nil
+	}
+}