Use file~timestamp.ext for version (fixes #1010)

internal/versioner/util.go

@@ -0,0 +1,42 @@
+// Copyright (C) 2014 The Syncthing Authors.
+//
+// This program is free software: you can redistribute it and/or modify it
+// under the terms of the GNU 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 General Public License for
+// more details.
+//
+// You should have received a copy of the GNU General Public License along
+// with this program. If not, see <http://www.gnu.org/licenses/>.
+
+package versioner
+
+import (
+	"path/filepath"
+	"regexp"
+)
+
+// Inserts ~tag just before the extension of the filename.
+func taggedFilename(name, tag string) string {
+	dir, file := filepath.Dir(name), filepath.Base(name)
+	ext := filepath.Ext(file)
+	withoutExt := file[:len(file)-len(ext)]
+	return filepath.Join(dir, withoutExt+"~"+tag+ext)
+}
+
+var tagExp = regexp.MustCompile(`~([^~.]+)(?:\.[^.]+)?$`)
+
+// Returns the tag from a filename, whether at the end or middle.
+func filenameTag(path string) string {
+	match := tagExp.FindStringSubmatch(path)
+	// match is []string{"whole match", "submatch"} when successfull
+
+	if len(match) != 2 {
+		return ""
+	}
+	return match[1]
+}