resources: file: Implement file attributes

Add owner which must be username or uid of the file owner, group which is
the group name or gid of the file, and mode which is the octal unix file
permissions.

Add separate implementation for Go 1.6 and lower.

resources/file_attrs.go

@@ -0,0 +1,43 @@
+// Mgmt
+// Copyright (C) 2013-2016+ James Shubin and the project contributors
+// Written by James Shubin <james@shubin.ca> and the project contributors
+//
+// This program is free software: you can redistribute it and/or modify
+// it under the terms of the GNU Affero General Public License as published by
+// the Free Software Foundation, either version 3 of the License, or
+// (at your option) any later version.
+//
+// This program is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+// GNU Affero General Public License for more details.
+//
+// You should have received a copy of the GNU Affero General Public License
+// along with this program.  If not, see <http://www.gnu.org/licenses/>.
+
+// +build go1.7
+
+package resources
+
+import (
+	"os/user"
+	"strconv"
+
+	errwrap "github.com/pkg/errors"
+)
+
+// gid returns the group id for the group specified in the yaml file graph.
+// Caller should first check obj.Group is not empty
+func (obj *FileRes) gid() (int, error) {
+	g2, err2 := user.LookupGroupId(obj.Group)
+	if err2 == nil {
+		return strconv.Atoi(g2.Gid)
+	}
+
+	g, err := user.LookupGroup(obj.Group)
+	if err == nil {
+		return strconv.Atoi(g.Gid)
+	}
+
+	return -1, errwrap.Wrapf(err, "Group lookup error (%s)", obj.Group)
+}