filelist/initramfs: add new type for slurping up file listers

internal/filelist/initramfs/initramfs.go

@@ -0,0 +1,34 @@
+package initramfs
+
+import (
+	"gitlab.com/postmarketOS/postmarketos-mkinitfs/internal/filelist"
+)
+
+// Initramfs allows building arbitrarily complex lists of features, by slurping
+// up types that implement FileLister (which includes this type! yippee) and
+// combining the output from them.
+type Initramfs struct {
+	features []filelist.FileLister
+}
+
+// New returns a new Initramfs that generate a list of files based on the given
+// list of FileListers.
+func New(features []filelist.FileLister) *Initramfs {
+	return &Initramfs{
+		features: features,
+	}
+}
+
+func (i *Initramfs) List() (*filelist.FileList, error) {
+	files := filelist.NewFileList()
+
+	for _, f := range i.features {
+		list, err := f.List()
+		if err != nil {
+			return nil, err
+		}
+		files.Import(list)
+	}
+
+	return files, nil
+}