Add option to overwrites tags option with values specified in an file (#62)

Reviewed-on: https://codeberg.org/woodpecker-plugins/docker-buildx/pulls/62
Reviewed-by: qwerty287 <qwerty287@noreply.codeberg.org>

cmd/docker-buildx/config.go

@@ -121,6 +121,12 @@ func settingsFlags(settings *plugin.Settings) []cli.Flag {
 			FilePath:    ".tags",
 			Destination: &settings.Build.Tags,
 		},
+		&cli.StringFlag{
+			Name:        "tags.file",
+			EnvVars:     []string{"PLUGIN_TAGS_FILE", "PLUGIN_TAG_FILE"},
+			Usage:       "overwrites tags flag with values find in set file",
+			Destination: &settings.Build.TagsFile,
+		},
 		&cli.BoolFlag{
 			Name:        "tags.auto",
 			EnvVars:     []string{"PLUGIN_AUTO_TAG"},