sources/rootfs: Support local image files

doc/source.md

@@ -36,7 +36,7 @@ It needs to be one of
 * voidlinux-http
 
 The `url` field defines the URL or mirror of the rootfs image.
-Although this field is not required, most downloaders will need it.
+Although this field is not required, most downloaders will need it. The `rootfs-http` downloader also supports local image files when prefixed with `file://`, e.g. `url: file:///home/user/image.tar.gz` or `url: file:///home/user/image.squashfs`.
 
 The `keys` field is a list of GPG keys.
 These keys can be listed as fingerprints or armored keys.

sources/rootfs-http.go

@@ -2,6 +2,7 @@ package sources
 
 import (
 	"fmt"
+	"net/url"
 	"path"
 	"path/filepath"
 
@@ -15,17 +16,33 @@ type rootfs struct {
 
 // Run downloads a tarball.
 func (s *rootfs) Run() error {
-	fpath, err := shared.DownloadHash(s.definition.Image, s.definition.Source.URL, "", nil)
+	URL, err := url.Parse(s.definition.Source.URL)
 	if err != nil {
-		return fmt.Errorf("Failed to download %q: %w", s.definition.Source.URL, err)
+		return fmt.Errorf("Failed to parse URL: %w", err)
 	}
 
-	s.logger.Infow("Unpacking image", "file", filepath.Join(fpath, path.Base(s.definition.Source.URL)))
+	var fpath string
+	var filename string
+
+	if URL.Scheme == "file" {
+		fpath = filepath.Dir(URL.Path)
+		filename = filepath.Base(URL.Path)
+	} else {
+		fpath, err = shared.DownloadHash(s.definition.Image, s.definition.Source.URL, "", nil)
+		if err != nil {
+			return fmt.Errorf("Failed to download %q: %w", s.
+				definition.Source.URL, err)
+		}
+
+		filename = path.Base(s.definition.Source.URL)
+	}
+
+	s.logger.Infow("Unpacking image", "file", filepath.Join(fpath, filename))
 
 	// Unpack
-	err = lxd.Unpack(filepath.Join(fpath, path.Base(s.definition.Source.URL)), s.rootfsDir, false, false, nil)
+	err = lxd.Unpack(filepath.Join(fpath, filename), s.rootfsDir, false, false, nil)
 	if err != nil {
-		return fmt.Errorf("Failed to unpack %q: %w", filepath.Join(fpath, path.Base(s.definition.Source.URL)), err)
+		return fmt.Errorf("Failed to unpack %q: %w", filepath.Join(fpath, filename), err)
 	}
 
 	return nil