fix prune when based on counting

Signed-off-by: Avi Deitcher <avi@deitcher.net>

Author: deitch

pkg/core/prune.go

@@ -122,7 +122,7 @@ func pruneTarget(ctx context.Context, logger *logrus.Entry, target storage.Stora
 			return 0
 		})
 		slices.Reverse(filesWithTimes)
-		if retainCount >= len(filesWithTimes) {
+		if retainCount < len(filesWithTimes) {
 			for i := 0 + retainCount; i < len(filesWithTimes); i++ {
 				logger.Debugf("Adding candidate file %s:", filesWithTimes[i].filename)
 				candidates = append(candidates, filesWithTimes[i].filename)

pkg/core/prune_test.go

@@ -69,6 +69,8 @@ func TestPrune(t *testing.T) {
 		safefilename := fmt.Sprintf("db_backup_%sZ.gz", relativeTime.Format("2006-01-02T15-04-05"))
 		safefilenames = append(safefilenames, safefilename)
 	}
+	t.Log(filenames)
+	t.Log(filenames[0:2])
 	tests := []struct {
 		name        string
 		opts        PruneOptions
@@ -87,6 +89,9 @@ func TestPrune(t *testing.T) {
 		{"2 days", PruneOptions{Retention: "2d", Now: now}, filenames, filenames[0:6], nil},
 		// 3 weeks - file[13] is 504h+30m = 504.5h, so it should be pruned
 		{"3 weeks", PruneOptions{Retention: "3w", Now: now}, filenames, filenames[0:13], nil},
+		// 2 most recent files
+		{"2 most recent", PruneOptions{Retention: "2c", Now: now}, filenames, filenames[0:2], nil},
+
 		// repeat for safe file names
 		{"1 hour safe names", PruneOptions{Retention: "1h", Now: now}, safefilenames, safefilenames[0:1], nil},
 		// 2 hours - file[2] is 2h+30m = 2.5h, so it should be pruned
@@ -148,6 +153,8 @@ func TestPrune(t *testing.T) {
 			}
 			slices.Sort(afterFiles)
 			slices.Sort(tt.afterFiles)
+			t.Logf("expected files: %v", tt.afterFiles)
+			t.Logf("after files: %v", afterFiles)
 			assert.ElementsMatch(t, tt.afterFiles, afterFiles)
 		})
 	}