replace dockerfile/dockerignore with patternmatcher/ignorefile

The BuildKit dockerignore package was integrated in the patternmatcher
repository / module. This patch updates our uses of the BuildKit package
with its new location.

A small local change was made to keep the format of the existing error message,
because the "ignorefile" package is slightly more agnostic in that respect
and doesn't include ".dockerignore" in the error message.

Signed-off-by: Sebastiaan van Stijn <github@gone.nl>

builder/remotecontext/detect.go

@@ -16,9 +16,9 @@ import (
 	"github.com/docker/docker/builder/remotecontext/urlutil"
 	"github.com/docker/docker/errdefs"
 	"github.com/docker/docker/pkg/containerfs"
-	"github.com/moby/buildkit/frontend/dockerfile/dockerignore"
 	"github.com/moby/buildkit/frontend/dockerfile/parser"
 	"github.com/moby/patternmatcher"
+	"github.com/moby/patternmatcher/ignorefile"
 	"github.com/pkg/errors"
 )
 
@@ -124,10 +124,10 @@ func removeDockerfile(c modifiableContext, filesToRemove ...string) error {
 	case err != nil:
 		return err
 	}
-	excludes, err := dockerignore.ReadAll(f)
+	excludes, err := ignorefile.ReadAll(f)
 	if err != nil {
 		f.Close()
-		return err
+		return errors.Wrap(err, "error reading .dockerignore")
 	}
 	f.Close()
 	filesToRemove = append([]string{".dockerignore"}, filesToRemove...)

vendor/github.com/moby/patternmatcher/ignorefile/ignorefile.go

@@ -0,0 +1,73 @@
+package ignorefile
+
+import (
+	"bufio"
+	"bytes"
+	"io"
+	"path/filepath"
+	"strings"
+)
+
+// ReadAll reads an ignore file from a reader and returns the list of file
+// patterns to ignore, applying the following rules:
+//
+//   - An UTF8 BOM header (if present) is stripped.
+//   - Lines starting with "#" are considered comments and are skipped.
+//
+// For remaining lines:
+//
+//   - Leading and trailing whitespace is removed from each ignore pattern.
+//   - It uses [filepath.Clean] to get the shortest/cleanest path for
+//     ignore patterns.
+//   - Leading forward-slashes ("/") are removed from ignore patterns,
+//     so "/some/path" and "some/path" are considered equivalent.
+func ReadAll(reader io.Reader) ([]string, error) {
+	if reader == nil {
+		return nil, nil
+	}
+
+	var excludes []string
+	currentLine := 0
+	utf8bom := []byte{0xEF, 0xBB, 0xBF}
+
+	scanner := bufio.NewScanner(reader)
+	for scanner.Scan() {
+		scannedBytes := scanner.Bytes()
+		// We trim UTF8 BOM
+		if currentLine == 0 {
+			scannedBytes = bytes.TrimPrefix(scannedBytes, utf8bom)
+		}
+		pattern := string(scannedBytes)
+		currentLine++
+		// Lines starting with # (comments) are ignored before processing
+		if strings.HasPrefix(pattern, "#") {
+			continue
+		}
+		pattern = strings.TrimSpace(pattern)
+		if pattern == "" {
+			continue
+		}
+		// normalize absolute paths to paths relative to the context
+		// (taking care of '!' prefix)
+		invert := pattern[0] == '!'
+		if invert {
+			pattern = strings.TrimSpace(pattern[1:])
+		}
+		if len(pattern) > 0 {
+			pattern = filepath.Clean(pattern)
+			pattern = filepath.ToSlash(pattern)
+			if len(pattern) > 1 && pattern[0] == '/' {
+				pattern = pattern[1:]
+			}
+		}
+		if invert {
+			pattern = "!" + pattern
+		}
+
+		excludes = append(excludes, pattern)
+	}
+	if err := scanner.Err(); err != nil {
+		return nil, err
+	}
+	return excludes, nil
+}

vendor/modules.txt

@@ -790,6 +790,7 @@ github.com/moby/locker
 # github.com/moby/patternmatcher v0.6.0
 ## explicit; go 1.19
 github.com/moby/patternmatcher
+github.com/moby/patternmatcher/ignorefile
 # github.com/moby/pubsub v1.0.0
 ## explicit; go 1.19
 github.com/moby/pubsub