archive,hookfiles: convert paths to usr-merge when necessary (MR 39)

Co-authored-by: Caleb Connolly <caleb@postmarketos.org>

internal/archive/archive.go

@@ -237,7 +237,10 @@ func (archive *Archive) AddItemsExclude(flister filelist.FileLister, exclude fil
 
 // Adds the given file or directory at "source" to the archive at "dest"
 func (archive *Archive) AddItem(source string, dest string) error {
-
+	if osutil.HasMergedUsr() {
+		source = osutil.MergeUsr(source)
+		dest = osutil.MergeUsr(dest)
+	}
 	sourceStat, err := os.Lstat(source)
 	if err != nil {
 		e, ok := err.(*os.PathError)

internal/filelist/hookfiles/hookfiles.go

@@ -11,6 +11,7 @@ import (
 
 	"gitlab.com/postmarketOS/postmarketos-mkinitfs/internal/filelist"
 	"gitlab.com/postmarketOS/postmarketos-mkinitfs/internal/misc"
+	"gitlab.com/postmarketOS/postmarketos-mkinitfs/internal/osutil"
 )
 
 type HookFiles struct {
@@ -64,6 +65,9 @@ func slurpFiles(fd io.Reader) (*filelist.FileList, error) {
 		}
 
 		src, dest, has_dest := strings.Cut(line, ":")
+		if osutil.HasMergedUsr() {
+			src = osutil.MergeUsr(src)
+		}
 
 		fFiles, err := misc.GetFiles([]string{src}, true)
 		if err != nil {

internal/osutil/osutil.go

@@ -27,6 +27,27 @@ func HasMergedUsr() bool {
 	return true
 }
 
+// Converts given path to one supported by a merged /usr config.
+// E.g., /bin/foo becomes /usr/bin/foo, /lib/bar becomes /usr/lib/bar
+// See: https://www.freedesktop.org/wiki/Software/systemd/TheCaseForTheUsrMerge
+func MergeUsr(file string) string {
+
+	// Prepend /usr to supported paths
+	for _, prefix := range []string{"/bin", "/sbin", "/lib", "/lib64"} {
+		if strings.HasPrefix(file, prefix) {
+			file = filepath.Join("/usr", file)
+			break
+		}
+	}
+
+	// Convert /usr/sbin --> /usr/bin
+	if part, found := strings.CutPrefix(file, "/usr/sbin"); found {
+		file = filepath.Join("/usr/bin/", part)
+	}
+
+	return file
+}
+
 // Converts a relative symlink target path (e.g. ../../lib/foo.so), that is
 // absolute path
 func RelativeSymlinkTargetToDir(symPath string, dir string) (string, error) {

internal/osutil/osutil_test.go

@@ -0,0 +1,49 @@
+// Copyright 2024 Clayton Craft <clayton@craftyguy.net>
+// SPDX-License-Identifier: GPL-3.0-or-later
+
+package osutil
+
+import (
+	"testing"
+)
+
+func TestMergeUsr(t *testing.T) {
+	subtests := []struct {
+		in       string
+		expected string
+	}{
+		{
+			in:       "/bin/foo",
+			expected: "/usr/bin/foo",
+		},
+		{
+			in:       "/sbin/foo",
+			expected: "/usr/bin/foo",
+		},
+		{
+			in:       "/usr/sbin/foo",
+			expected: "/usr/bin/foo",
+		},
+		{
+			in:       "/usr/bin/foo",
+			expected: "/usr/bin/foo",
+		},
+		{
+			in:       "/lib/foo.so",
+			expected: "/usr/lib/foo.so",
+		},
+		{
+			in:       "/lib64/foo.so",
+			expected: "/usr/lib64/foo.so",
+		},
+	}
+
+	for _, st := range subtests {
+		t.Run(st.in, func(t *testing.T) {
+			out := MergeUsr(st.in)
+			if out != st.expected {
+				t.Fatalf("expected: %q, got: %q\n", st.expected, out)
+			}
+		})
+	}
+}