fix: correct series file entries and sort patch keys in deb target

Fix two bugs in the deb patch handling:
1. sourcePatchesDir wrote the target source name instead of the patch
   source name to the series file, causing incorrect documentation.
2. createPatchScript iterated over the Patches map without sorting,
   causing non-deterministic patch application order unlike the RPM
   target which sorts keys.

Add unit tests for both issues.

Signed-off-by: Burak Ok <burakok@microsoft.com>

Author: burak-ok

packaging/linux/deb/debroot.go

@@ -67,7 +67,7 @@ func sourcePatchesDir(sOpt dalec.SourceOpts, base llb.State, dir, name string, s
 		st := src.ToState(patchStateName, sOpt, opts...)
 
 		st = base.File(llb.Copy(st, copySrc, filepath.Join(patchesPath, patch.Source)), opts...)
-		seriesBuf.WriteString(name + "\n")
+		seriesBuf.WriteString(patch.Source + "\n")
 		states = append(states, st)
 	}
 
@@ -343,8 +343,9 @@ func createPatchScript(spec *dalec.Spec, cfg *SourcePkgConfig) []byte {
 
 	writeScriptHeader(buf, cfg)
 
-	for name, patches := range spec.Patches {
-		for _, patch := range patches {
+	sorted := dalec.SortMapKeys(spec.Patches)
+	for _, name := range sorted {
+		for _, patch := range spec.Patches[name] {
 			p := filepath.Join("${DEBIAN_DIR:=debian}/dalec/patches", name, patch.Source)
 			fmt.Fprintf(buf, "patch -d %q -p%d -s < %q\n", name, *patch.Strip, p)
 		}

packaging/linux/deb/debroot_patch_test.go

@@ -0,0 +1,103 @@
+package deb
+
+import (
+	"bytes"
+	"context"
+	"path/filepath"
+	"strings"
+	"testing"
+
+	"github.com/moby/buildkit/client/llb"
+	"github.com/project-dalec/dalec"
+	"gotest.tools/v3/assert"
+)
+
+func intPtr(i int) *int {
+	return &i
+}
+
+func TestCreatePatchScript_MultiplePatchesSorted(t *testing.T) {
+	t.Parallel()
+
+	spec := &dalec.Spec{
+		Patches: map[string][]dalec.PatchSpec{
+			"src-b": {
+				{Source: "patch-b1", Strip: intPtr(1)},
+			},
+			"src-a": {
+				{Source: "patch-a1", Strip: intPtr(1)},
+				{Source: "patch-a2", Strip: intPtr(1)},
+			},
+		},
+	}
+
+	got := string(createPatchScript(spec, nil))
+
+	// Patches should be sorted by the source name being patched (the key in Patches map)
+	// to ensure deterministic ordering, matching RPM behavior.
+	idxA := strings.Index(got, `patch -d "src-a"`)
+	idxB := strings.Index(got, `patch -d "src-b"`)
+
+	assert.Assert(t, idxA >= 0, "expected patch command for src-a, got:\n%s", got)
+	assert.Assert(t, idxB >= 0, "expected patch command for src-b, got:\n%s", got)
+	assert.Assert(t, idxA < idxB, "expected src-a patches before src-b patches for deterministic ordering, got:\n%s", got)
+
+	// Verify all patch commands are present
+	assert.Assert(t, strings.Contains(got, "patch-a1"), "expected patch-a1 reference in script, got:\n%s", got)
+	assert.Assert(t, strings.Contains(got, "patch-a2"), "expected patch-a2 reference in script, got:\n%s", got)
+	assert.Assert(t, strings.Contains(got, "patch-b1"), "expected patch-b1 reference in script, got:\n%s", got)
+}
+
+func TestSourcePatchesDir_SeriesContainsPatchSourceNames(t *testing.T) {
+	t.Parallel()
+
+	spec := &dalec.Spec{
+		Sources: map[string]dalec.Source{
+			"my-patch1": {
+				Inline: &dalec.SourceInline{
+					File: &dalec.SourceInlineFile{
+						Contents: "patch1 content",
+					},
+				},
+			},
+			"my-patch2": {
+				Inline: &dalec.SourceInline{
+					File: &dalec.SourceInlineFile{
+						Contents: "patch2 content",
+					},
+				},
+			},
+		},
+		Patches: map[string][]dalec.PatchSpec{
+			"my-src": {
+				{Source: "my-patch1", Strip: intPtr(1)},
+				{Source: "my-patch2", Strip: intPtr(1)},
+			},
+		},
+	}
+
+	ctx := context.Background()
+	base := llb.Scratch().File(llb.Mkdir("patches", 0o755))
+	states := sourcePatchesDir(dalec.SourceOpts{}, base, "patches", "my-src", spec)
+
+	// The last state should be the series file
+	seriesState := states[len(states)-1]
+	def, err := seriesState.Marshal(ctx)
+	assert.NilError(t, err)
+
+	// Find the series file in the definition and verify its contents
+	mkfile, err := findMkfile(t, def.ToPB(), filepath.Join("/patches", "my-src", "series"))
+	assert.NilError(t, err)
+	assert.Assert(t, mkfile != nil, "series file not found in the state definition")
+
+	// The series file should contain the patch source names, not the target name
+	content := string(mkfile.Data)
+	lines := strings.Split(strings.TrimSpace(content), "\n")
+	assert.Assert(t, len(lines) == 2, "expected 2 lines in series file, got %d: %q", len(lines), content)
+	assert.Assert(t, lines[0] == "my-patch1", "expected first line to be 'my-patch1', got %q", lines[0])
+	assert.Assert(t, lines[1] == "my-patch2", "expected second line to be 'my-patch2', got %q", lines[1])
+
+	// Verify it does NOT contain the target source name repeated
+	assert.Assert(t, !bytes.Contains(mkfile.Data, []byte("my-src")),
+		"series file should contain patch source names, not the target source name 'my-src', got: %q", content)
+}