internal/pkg: rename archive checksum helpers

These names are more consistent with other helper names, so rename them while the API is still internal.

Signed-off-by: Ophestra <cat@gensokyo.uk>

internal/pkg/archive.go

@@ -262,8 +262,8 @@ func Write(fsys fs.FS, root string, w io.Writer) error {
 	return aw.Close()
 }
 
-// HashFS returns a checksum produced by hashing the result of [Flatten].
-func HashFS(buf *Checksum, fsys fs.FS, root string) error {
+// SumFS saves checksum of the archive of fsys to the value pointed to by buf.
+func SumFS(buf *Checksum, fsys fs.FS, root string) error {
 	h := sha512.New384()
 	if err := Write(fsys, root, h); err != nil {
 		return err
@@ -272,7 +272,8 @@ func HashFS(buf *Checksum, fsys fs.FS, root string) error {
 	return nil
 }
 
-// HashDir returns a checksum produced by hashing the result of [Flatten].
-func HashDir(buf *Checksum, pathname *check.Absolute) error {
-	return HashFS(buf, os.DirFS(pathname.String()), ".")
+// SumDir saves checksum of the archive of directory at pathname to the value
+// pointed to by buf.
+func SumDir(buf *Checksum, pathname *check.Absolute) error {
+	return SumFS(buf, os.DirFS(pathname.String()), ".")
 }