Refuse a relative file:// storage_url and decode its escapes (closes #299)

The path after file:// was used as written. file://dest resolved
against the working directory, so a backup run from another directory
wrote elsewhere, exited 0 and left a snapshot that could not be
restored; my%20stick created a directory with that literal name.

Config load now refuses a file:// storage_url whose path is not
absolute. ParseStorageURL refuses it too and decodes percent-escapes;
a literal space still works. The rule is written in both packages
because config cannot import storage, which imports config.

A % not followed by two hex digits now fails when the storage is
opened, not at config load.

Model: opus-5-5

TODO.md

@@ -22,7 +22,7 @@ the tag exists and is exercised; what is left is merging `next` to
 
 # Completed Steps
 
-- 2026-10-13: Refused a `file://` `storage_url` whose path is relative
+- 2026-10-12: Refused a `file://` `storage_url` whose path is relative
   ([issue #299](https://git.eeqj.de/sneak/vaultik/issues/299)). The text
   after `file://` was used as written, so `file://dest` resolved against
   the working directory: a backup run from another directory wrote to a
@@ -33,16 +33,6 @@ the tag exists and is exercised; what is left is merging `next` to
   creating one named `my%20stick`; a path written with a literal space
   works as before.
 
-- 2026-10-12: Rejected a retention duration longer than about 292 years
-  ([issue #289](https://git.eeqj.de/sneak/vaultik/issues/289)). The
-  number given to `--older-than` or `--keep-newer-than` was multiplied
-  by the length of its unit with no limit, so from `293y`, `15251w`,
-  `3559mo` or `106752d`, or a sum of parts such as `200y200y`, the
-  result wrapped to a negative duration. The cutoff then lay in the
-  future, every snapshot of the name was deleted, the one just made
-  included, and the command exited 0. Such a duration is now rejected
-  as invalid and nothing is deleted.
-
 - 2026-10-08: Made a backup cancelled under `--skip-errors` stop at once
   ([issue #286](https://git.eeqj.de/sneak/vaultik/issues/286)). After
   Ctrl-C or SIGTERM, phase 2 treated the cancellation error from each

internal/storage/url_parse_test.go

@@ -14,10 +14,7 @@ import (
 func TestParseStorageURLValid(t *testing.T) {
 	t.Parallel()
 
-	const (
-		bucket     = "mybucket"
-		fileScheme = "file"
-	)
+	const bucket = "mybucket"
 
 	cases := []struct {
 		name string
@@ -27,17 +24,17 @@ func TestParseStorageURLValid(t *testing.T) {
 		{
 			name: "file absolute path",
 			raw:  "file:///var/backups/vaultik",
-			want: &storage.URL{Scheme: fileScheme, Prefix: "/var/backups/vaultik"},
+			want: &storage.URL{Scheme: "file", Prefix: "/var/backups/vaultik"},
 		},
 		{
 			name: "file percent-escaped path is decoded",
 			raw:  "file:///Volumes/my%20stick/backup",
-			want: &storage.URL{Scheme: fileScheme, Prefix: "/Volumes/my stick/backup"},
+			want: &storage.URL{Scheme: "file", Prefix: "/Volumes/my stick/backup"},
 		},
 		{
 			name: "file path with a literal space",
 			raw:  "file:///Volumes/my stick/backup",
-			want: &storage.URL{Scheme: fileScheme, Prefix: "/Volumes/my stick/backup"},
+			want: &storage.URL{Scheme: "file", Prefix: "/Volumes/my stick/backup"},
 		},
 		{
 			name: "s3 bucket and prefix, ssl defaults on",

internal/vaultik/helpers.go

@@ -3,7 +3,6 @@ package vaultik
 import (
 	"errors"
 	"fmt"
-	"math"
 	"regexp"
 	"strconv"
 	"strings"
@@ -48,10 +47,6 @@ const (
 	year  = 365 * day
 )
 
-// maxDuration is the largest value a time.Duration can hold, about 292
-// years.
-const maxDuration = time.Duration(math.MaxInt64)
-
 // A snapshot ID split on "_" has at least a hostname and a trailing
 // timestamp.
 const minSnapshotIDParts = 2
@@ -150,10 +145,10 @@ func parseSnapshotName(snapshotID, hostname string) string {
 // parseDuration parses a duration string with support for human-friendly units:
 // d/day/days, w/week/weeks, mo/month/months, y/year/years, plus standard Go
 // duration units. Following Go, m is minutes and mo is months. A bare number,
-// an unknown unit, a negative value, and a total longer than maxDuration are
-// all rejected. Outside the Go units the input must be whole numbers each
-// followed directly by a unit (2w3d), so 1.0y and 30 days are errors;
-// decimals work only in Go units (1.5h).
+// an unknown unit, and a negative value are all rejected. Outside the Go
+// units the input must be whole numbers each followed directly by a unit
+// (2w3d), so 1.0y and 30 days are errors; decimals work only in Go units
+// (1.5h).
 func parseDuration(s string) (time.Duration, error) {
 	if strings.HasPrefix(strings.TrimSpace(s), "-") {
 		return 0, errNegativeDuration
@@ -186,30 +181,19 @@ func parseDuration(s string) (time.Duration, error) {
 			return 0, fmt.Errorf("invalid number %q: %w", match[1], err)
 		}
 
-		var unitLength time.Duration
-
 		unit := strings.ToLower(match[2])
 		switch unit {
 		case "d", "day", "days":
-			unitLength = day
+			total += time.Duration(n) * day
 		case "w", "week", "weeks":
-			unitLength = week
+			total += time.Duration(n) * week
 		case "mo", "month", "months":
-			unitLength = month
+			total += time.Duration(n) * month
 		case "y", "year", "years":
-			unitLength = year
+			total += time.Duration(n) * year
 		default:
 			return 0, fmt.Errorf("%w %q", errUnknownTimeUnit, unit)
 		}
-
-		// Past maxDuration the sum wraps to a negative value, which would
-		// put the purge cutoff in the future.
-		if time.Duration(n) > (maxDuration-total)/unitLength {
-			return 0, fmt.Errorf("%w: %q is longer than about 292 years",
-				errInvalidDuration, s)
-		}
-
-		total += time.Duration(n) * unitLength
 	}
 
 	return total, nil

internal/vaultik/helpers_test.go

@@ -111,17 +111,6 @@ func TestParseDuration(t *testing.T) {
 		{"30 days", 0, true},
 		{"30 days ago", 0, true},
 		{"x7d", 0, true},
-		// The largest time.Duration is about 292 years. A larger value
-		// must be rejected, not wrapped to a negative one, which would
-		// put the cutoff in the future and select every snapshot.
-		{"292y", 292 * 365 * 24 * time.Hour, false},
-		{"293y", 0, true},
-		{"3559mo", 0, true},
-		{"15251w", 0, true},
-		{"106752d", 0, true},
-		{"2562048h", 0, true},
-		{"200y200y", 0, true},
-		{"292y6mo", 0, true},
 	}
 
 	for _, tt := range tests {

internal/vaultik/purge_per_name_test.go

@@ -267,29 +267,6 @@ func TestPurgeOlderThan_WithNameFilter(t *testing.T) {
 	assert.Contains(t, remaining, snapHomeT0)
 }
 
-func TestPurgeOlderThan_TooLargeDeletesNothing(t *testing.T) {
-	log.Initialize(log.Config{})
-	t.Parallel()
-
-	snapshotIDs := []string{snapHomeT0, snapHomeT1}
-
-	v := setupPurgeTest(t, snapHostname, snapshotIDs)
-
-	err := v.PurgeSnapshotsWithOptions(&vaultik.SnapshotPurgeOptions{
-		OlderThan: "1000y",
-		Force:     true,
-	})
-	require.Error(t, err)
-
-	err = v.PurgeSnapshotsWithOptions(&vaultik.SnapshotPurgeOptions{
-		OlderThan: "292y",
-		Force:     true,
-	})
-	require.NoError(t, err)
-
-	assert.ElementsMatch(t, snapshotIDs, listRemainingSnapshots(t, v))
-}
-
 func TestPurgeKeepLatest_ThreeNames(t *testing.T) {
 	log.Initialize(log.Config{})
 	t.Parallel()