Update README.md

Author: szotsaki

README.md

@@ -1,2 +1,12 @@
-# svn-backup
+# SVN backup
 Lightweight script for SVN backup
+
+This script creates complete SVN dumps of all repositories within `$repo_dir` to `$backup_dir`.
+Backup is only made when the repo revision is greater than the one of the previous backup.
+
+Only one backup of a repo is kept.
+
+The script implies that the repository names are "prefix codes", i.e. none of
+their names begin with an other repo name (eg. "test" and "test-2")
+
+Compression is made with XZ (LZMA 2).