Clearify how to remove backups after a while

README.md

@@ -70,14 +70,21 @@ On macOS, it has a few disadvantages compared to Time Machine - in particular it
 
 ## Backup expiration logic
 
-Backup sets are automatically deleted following a simple expiration strategy defined with the `--strategy` flag. This strategy is a series of time intervals with each item being defined as `x:y`, which means "after x days, keep one backup every y days". The default strategy is `1:1 30:7 365:30`, which means:
+Backup sets are automatically deleted following a simple expiration strategy defined with the `--strategy` flag. This strategy is a series of time intervals with each item being defined as `x:y`, which means "after x days, keep one backup every y days". The value y can either be a positive integer or the character `x`.
+
+ The default strategy is `1:1 30:7 365:30`, which means:
 
 - After **1** day, keep one backup every **1** day (**1:1**).
 - After **30** days, keep one backup every **7** days (**30:7**).
 - After **365** days, keep one backup every **30** days (**365:30**).
 
 Before the first interval (i.e. by default within the first 24h) it is implied that all backup sets are kept. Additionally, if the backup destination directory is full, the oldest backups are deleted until enough space is available.
 
+An example of a backup strategy using `x` is givne by `1:1 50:x`, which means:
+
+- After **1** day, keep one backup every **1** day (**1:1**).
+- After **50** days, no longer keep backups.
+
 ## Exclusion file
 
 An optional exclude file can be provided as a third parameter. It should be compatible with the `--exclude-from` parameter of rsync. See [this tutorial](https://sites.google.com/site/rsync2u/home/rsync-tutorial/the-exclude-from-option) for more information.

rsync_tmbackup.sh

@@ -116,8 +116,8 @@ fn_expire_backups() {
 			# If we've found the strategy token that applies to this backup
 			if [ "$backup_timestamp" -le "$cut_off_timestamp" ]; then
 
-				# Special case: if Y is "0" we delete every time
-				if [ $cut_off_interval -eq "0" ]; then
+				# Special case: if Y is "0", "x" or "X" we delete every time
+				if [[ ($cut_off_interval -eq "0") || ($cut_off_interval -eq "x") || ($cut_off_interval -eq "X") ]]; then
 					fn_expire_backup "$backup_dir"
 					break
 				fi

tests/populate_dest.php

@@ -21,6 +21,9 @@
 	throw new Exception('Not implemented');
 }
 
+mkdir($destDir);
+touch($destDir . '/backup.marker');
+
 $d = new DateTime();
 $d->sub(new DateInterval('P' . $totalDays . 'D'));
 

tests/test_expiration_of_zero.php

@@ -0,0 +1,42 @@
+<?php 
+
+$backupDirectory = './TestDest/';
+
+chdir(__DIR__);
+
+exec('rm -rf ./TestDest');
+
+include 'populate_dest.php';
+
+exec('../rsync_tmbackup.sh --strategy "1:1 30:x" ./TestSource/ ' . $backupDirectory, $output, $return);
+
+if ($return !== 0) {
+    echo 'Invalid return code';
+    echo implode(PHP_EOL, $output);
+    exit(1);
+}
+
+$backups = array_filter(
+    scandir($backupDirectory),
+    function ($file) use ($backupDirectory) {
+        return is_dir($backupDirectory . $file) && !in_array($file, ['.', '..']);
+    }
+);
+
+$expected = 33;
+if (count($backups) !== $expected) {
+    echo 'Given this strategy there should be ' . $expected . ' directories. But ' . count($backups) . ' directories found.';
+    echo 'Found directories:';
+    echo implode(
+        PHP_EOL, 
+        array_map(
+            function ($directory) { return "- {$directory}"; },
+            $backups
+        )
+    );
+
+    exit(1);
+}
+
+echo 'All assertions succeeded';
+exit(0);