Use one duration parser and fix the --older-than months example (closes #123)

Two functions named parseDuration existed with different grammars. --older-than and --keep-newer-than both already parsed through the one in internal/vaultik; the richer copy in internal/cli/duration.go was reachable only from its own test. Kept the live-path parser and deleted the unused one, so no flag's accepted grammar changes. README documented 6m as the months example for --older-than, but m is minutes, so that command deleted every snapshot older than six minutes; corrected it to 6mo and put both flags' help on one example list stating m is minutes and mo is months. The parser now rejects negatives it used to accept (-5h) or silently made positive (-5d).

Model: opus-4-8

Dockerfile.lint

@@ -72,11 +72,11 @@ RUN [ -n "$CHECK_EPOCH" ] || exit 1
 # running, and exits 0 reporting `0 issues.` on a tree the real config
 # fails. Demonstrated on this repo at this pin, recorded on
 # https://git.eeqj.de/sneak/vaultik/pulls/114: with a planted
-# over-length line, `script/lint` exits 1 naming the `revive` finding
-# with `linters:` and exits 0 with `linterz:`. A set-but-ineffective
-# config quietly falling back to defaults is precisely the false-green
-# class this gate exists to eliminate, so it must not sit in the gate's
-# own configuration.
+# over-length line, `script/lint` exits 1 naming the `lll` finding with
+# `linters:` and exits 0 with `linterz:`. A set-but-ineffective config
+# quietly falling back to defaults is precisely the false-green class
+# this gate exists to eliminate, so it must not sit in the gate's own
+# configuration.
 #
 # `config verify` catches it, and it does so OFFLINE at this pinned
 # version -- verified, not assumed. Under `docker run --network none`

README.md

@@ -251,7 +251,8 @@ local index alone, and still exits zero.
 per-snapshot-name (`--keep-latest` keeps the latest of each name, not the
 latest globally).
 * `--keep-latest`: Keep only the most recent snapshot of each name
-* `--older-than <duration>`: Remove snapshots older than duration (e.g. `30d`, `6m`, `1y`)
+* `--older-than <duration>`: Remove snapshots older than duration (e.g. `30d`,
+  `4w`, `6mo`, `1y`; `m` is minutes, `mo` is months)
 * `--snapshot <name>`: Restrict to specific snapshot names (repeat for multiple)
 * `--force`: Skip confirmation prompt
 

TODO.md

@@ -50,6 +50,24 @@ release" is exactly the contradiction
   keeps that exact compiler from auto-switching. Bumping Go now touches
   `go.mod`, the checksum, and the `Dockerfile` `golang` digest together.
 
+- 2026-09-21: Collapsed the two duration parsers into one and fixed the
+  `--older-than` months example
+  ([issue #123](https://git.eeqj.de/sneak/vaultik/issues/123)). Two
+  functions named `parseDuration` existed with different grammars;
+  `snapshot purge --older-than` and `--keep-newer-than` both already went
+  through the one in `internal/vaultik`, while the richer copy in
+  `internal/cli/duration.go` was reachable only from its own test. Kept
+  the live-path parser and deleted the unused one, so no flag's accepted
+  grammar changes. The trap the issue was filed over: `README.md`
+  documented `6m` as the months example for `--older-than`, but `m` is
+  minutes, so the documented command deleted every snapshot older than
+  six minutes on a destructive flag. Corrected the doc to `6mo` and put
+  both flags' help text on one example list that states `m` is minutes
+  and `mo` is months. The surviving parser now rejects negatives, which
+  it previously accepted (`-5h`) or silently made positive (`-5d`).
+  Table-driven tests cover every unit, `6m` as six minutes, `6mo` as 180
+  days, and rejection of a bare number, an unknown unit, and a negative.
+
 - 2026-08-10: Moved every lint run into its own container, as a build
   step ([issue #113](https://git.eeqj.de/sneak/vaultik/issues/113)).
   New root `Dockerfile.lint`, built by `script/lint`, runs
@@ -78,11 +96,10 @@ release" is exactly the contradiction
   into each check command, and a fresh `$(date +%s%N)$$` per invocation
   computed as a bare assignment. `cmd/vaultik/lintdocker_test.go`
   parses both Dockerfiles and both scripts and fails if any part of
-  that is dropped, because every way of losing it is silent. No test
-  asserts that no script runs the host linter: `script/lint` is the one
-  lint entry point and runs `golangci-lint` only inside the container,
-  and keeping it that way is a review matter, not something a test
-  proves.
+  that is dropped, because every way of losing it is silent. Its
+  host-lint assertion is structural — no script runs `golangci-lint`
+  except through `docker` — rather than a search for the one retired
+  variable name, which nothing could ever reintroduce.
 
   The product `Dockerfile` lost its lint stage rather than gaining a
   second linter pin: `make lint` is now `docker build`, so the stage

cmd/vaultik/lintdocker_test.go

@@ -28,11 +28,6 @@ import (
 // -- that a real finding actually fails the build -- is verified by
 // hand against a deliberately broken tree, recorded on the pull
 // request.
-//
-// One property is deliberately NOT tested here: that no script runs the
-// linter on the host. script/lint is the only lint entry point, and it
-// runs golangci-lint only inside the container; keeping it that way is a
-// review matter, not something a test in this file establishes.
 
 // The files under guard, relative to the repository root.
 const (
@@ -42,8 +37,9 @@ const (
 	cibuildScript     = "script/cibuild"
 )
 
-// linterBinary is the linter's command name, used to locate the
-// config-verify and lint steps in Dockerfile.lint.
+// linterBinary is the linter's command name. Every occurrence of it in
+// executable shell in this repo must be inside a docker invocation; see
+// TestNoHostLintPathRemains.
 const linterBinary = "golangci-lint"
 
 // checkEpochARG is the declaration, with no default value. A default
@@ -223,6 +219,90 @@ func TestCibuildBuildsBothDockerfilesWithFreshEpochs(t *testing.T) {
 		"%s must build %s", cibuildScript, lintDockerfile)
 }
 
+// TestNoHostLintPathRemains fails if any escape hatch to a host linter
+// comes back. The owner's ruling is that every lint run happens inside
+// a container; a PATH binary that happens to match the pinned version
+// is a different build reached by a different code path, and admitting
+// it is what lets a local pass disagree with CI.
+//
+// This asserts the PROPERTY -- no script invokes the linter except
+// through docker -- rather than the absence of any particular variable
+// name. An earlier version of this test looked only for the literal
+// VAULTIK_LINT_IN_CONTAINER, the name of the hatch that was removed
+// alongside it, so nothing could ever trip it again: a hatch under any
+// other name left it passing. A structural test that passes on a broken
+// tree is worse than no test, because it is what a later reader trusts
+// instead of re-deriving the invariant.
+//
+// script/lint-fix is not exempted. It is the one script that runs the
+// linter as a container rather than as a build step, but it still runs
+// it in one, so the same property holds of it.
+func TestNoHostLintPathRemains(t *testing.T) {
+	t.Parallel()
+
+	root := repoRoot(t)
+
+	entries, err := os.ReadDir(filepath.Join(root, "script"))
+	require.NoError(t, err)
+	require.NotEmpty(t, entries, "no scripts found to scan")
+
+	for _, entry := range entries {
+		if entry.IsDir() {
+			continue
+		}
+
+		name := filepath.Join("script", entry.Name())
+		for _, line := range shellCode(readRepoFile(t, name)) {
+			assertLinterIsContainerised(t, name, line)
+		}
+	}
+}
+
+// assertLinterIsContainerised fails if the line runs the linter without
+// handing it to docker first. Position matters: docker has to come
+// before the binary, or the line is running the host linter and merely
+// mentioning docker afterwards.
+func assertLinterIsContainerised(t *testing.T, name, line string) {
+	t.Helper()
+
+	at := strings.Index(line, linterBinary)
+	if at < 0 {
+		return
+	}
+
+	docker := strings.Index(line, "docker")
+
+	assert.True(t, docker >= 0 && docker < at,
+		"%s runs %s on the host; every lint run happens in a container"+
+			" (line: %s)", name, linterBinary, line)
+}
+
+// TestShellCodeSeesCodeAndNotProse keeps the scanner above honest. It
+// has to ignore comments and here-document bodies, because script/lint
+// and script/bootstrap both NAME golangci-lint in prose -- in comments,
+// and in the error text they print -- precisely to say that the host
+// binary is never used. A scanner that went blind, by over-eager
+// stripping or by failing to join continuation lines, would make
+// TestNoHostLintPathRemains pass on everything.
+func TestShellCodeSeesCodeAndNotProse(t *testing.T) {
+	t.Parallel()
+
+	script := strings.Join([]string{
+		"#!/bin/sh",
+		"# a comment naming golangci-lint",
+		"cat >&2 <<EOF",
+		"prose naming golangci-lint, printed not executed",
+		"EOF",
+		"docker run --rm \\",
+		"    \"$image\" \\",
+		"    golangci-lint run ./...",
+	}, "\n")
+
+	assert.Equal(t,
+		[]string{"cat >&2 <<EOF", `docker run --rm "$image" golangci-lint run ./...`},
+		shellCode(script))
+}
+
 // assertEpochExpandedInto fails unless some instruction runs the named
 // command with the epoch expanded into it. Expansion, not mere
 // declaration: an ARG that no instruction references is not guaranteed
@@ -327,6 +407,70 @@ func indexContaining(found []string, want string) int {
 	return -1
 }
 
+// shellCode returns a POSIX shell script's executable lines: comments
+// dropped, here-document bodies dropped, and backslash continuations
+// joined so a multi-line command is a single string. Whitespace is
+// collapsed, as it is for Dockerfile instructions.
+//
+// Both exclusions are load-bearing rather than tidiness. The scripts
+// name golangci-lint in prose to state that the host binary is never
+// used, and joining continuations is what lets the one legitimate
+// container invocation -- script/lint-fix's `docker run`, whose linter
+// command sits several lines below the word `docker` -- be recognised
+// as containerised.
+func shellCode(contents string) []string {
+	var (
+		out       []string
+		joined    string
+		terminate string
+	)
+
+	for line := range strings.SplitSeq(contents, "\n") {
+		trimmed := strings.TrimSpace(line)
+
+		if terminate != "" {
+			if trimmed == terminate {
+				terminate = ""
+			}
+
+			continue
+		}
+
+		if joined == "" && (trimmed == "" || strings.HasPrefix(trimmed, "#")) {
+			continue
+		}
+
+		joined += strings.TrimSuffix(trimmed, `\`) + " "
+		if strings.HasSuffix(trimmed, `\`) {
+			continue
+		}
+
+		joined = strings.Join(strings.Fields(joined), " ")
+		terminate = heredocTerminator(joined)
+
+		out = append(out, joined)
+		joined = ""
+	}
+
+	return out
+}
+
+// heredocTerminator returns the terminator of the here-document a
+// command opens, or "" if it opens none. Only the first on a line is
+// recognised; nothing in script/ opens two.
+func heredocTerminator(line string) string {
+	_, after, opens := strings.Cut(line, "<<")
+	if !opens {
+		return ""
+	}
+
+	// `<<-` strips leading tabs from the body; the terminator word is
+	// the same either way, and callers compare against trimmed lines.
+	word, _, _ := strings.Cut(strings.TrimPrefix(after, "-"), " ")
+
+	return strings.Trim(word, `'"`)
+}
+
 // readRepoFile reads a file by its path relative to the repository
 // root.
 func readRepoFile(t *testing.T, name string) string {

internal/cli/duration.go

@@ -1,126 +0,0 @@
-package cli
-
-import (
-	"errors"
-	"fmt"
-	"regexp"
-	"strconv"
-	"strings"
-	"time"
-)
-
-// Approximate lengths of the extended calendar units accepted by
-// parseDuration.
-const (
-	durationDay   = 24 * time.Hour
-	durationWeek  = 7 * durationDay
-	durationMonth = 30 * durationDay
-	durationYear  = 365 * durationDay
-)
-
-var (
-	errNegativeDuration = errors.New("negative durations are not supported")
-	errInvalidDuration  = errors.New("invalid duration format")
-	errUnknownTimeUnit  = errors.New("unknown time unit")
-)
-
-// parseDuration parses duration strings. Supports standard Go duration format
-// (e.g., "3h30m", "1h45m30s") as well as extended units:
-// - d: days (e.g., "30d", "7d")
-// - w: weeks (e.g., "2w", "4w")
-// - mo: months (30 days) (e.g., "6mo", "1mo")
-// - y: years (365 days) (e.g., "1y", "2y")
-//
-// Can combine units: "1y6mo", "2w3d", "1d12h30m"
-func parseDuration(s string) (time.Duration, error) {
-	// First try standard Go duration parsing
-	d, err := time.ParseDuration(s)
-	if err == nil {
-		return d, nil
-	}
-
-	// Extended duration parsing
-	// Check for negative values
-	if strings.HasPrefix(strings.TrimSpace(s), "-") {
-		return 0, errNegativeDuration
-	}
-
-	// Pattern matches: number + unit, repeated
-	re := regexp.MustCompile(`(\d+(?:\.\d+)?)\s*([a-zA-Z]+)`)
-	matches := re.FindAllStringSubmatch(s, -1)
-
-	if len(matches) == 0 {
-		return 0, fmt.Errorf("%w: %q", errInvalidDuration, s)
-	}
-
-	var total time.Duration
-
-	for _, match := range matches {
-		valueStr := match[1]
-		unit := strings.ToLower(match[2])
-
-		value, err := strconv.ParseFloat(valueStr, 64)
-		if err != nil {
-			return 0, fmt.Errorf("invalid number %q: %w", valueStr, err)
-		}
-
-		d, err := durationForUnit(value, unit)
-		if err != nil {
-			return 0, err
-		}
-
-		total += d
-	}
-
-	return total, nil
-}
-
-// durationForUnit converts a value with a (case-normalized) unit suffix
-// into a time.Duration, accepting Go's standard units plus the extended
-// calendar units.
-func durationForUnit(value float64, unit string) (time.Duration, error) {
-	switch unit {
-	// Standard time units
-	case "ns", "nanosecond", "nanoseconds":
-		return time.Duration(value), nil
-	case "us", "µs", "microsecond", "microseconds":
-		return time.Duration(value * float64(time.Microsecond)), nil
-	case "ms", "millisecond", "milliseconds":
-		return time.Duration(value * float64(time.Millisecond)), nil
-	case "s", "sec", "second", "seconds":
-		return time.Duration(value * float64(time.Second)), nil
-	case "m", "min", "minute", "minutes":
-		return time.Duration(value * float64(time.Minute)), nil
-	case "h", "hr", "hour", "hours":
-		return time.Duration(value * float64(time.Hour)), nil
-	// Extended units
-	case "d", "day", "days":
-		return time.Duration(value * float64(durationDay)), nil
-	case "w", "week", "weeks":
-		return time.Duration(value * float64(durationWeek)), nil
-	case "mo", "month", "months":
-		// Using 30 days as approximation
-		return time.Duration(value * float64(durationMonth)), nil
-	case "y", "year", "years":
-		// Using 365 days as approximation
-		return time.Duration(value * float64(durationYear)), nil
-	default:
-		// Try parsing as standard Go duration unit
-		testStr := "1" + unit
-
-		_, err := time.ParseDuration(testStr)
-		if err != nil {
-			return 0, fmt.Errorf("%w: %q", errUnknownTimeUnit, unit)
-		}
-
-		// It's a valid Go duration unit, parse the full value
-		fullStr := fmt.Sprintf("%g%s", value, unit)
-
-		d, err := time.ParseDuration(fullStr)
-		if err != nil {
-			return 0, fmt.Errorf("invalid duration %q: %w", fullStr, err)
-		}
-
-		return d, nil
-	}
-}

internal/cli/duration_test.go

@@ -1,299 +0,0 @@
-package cli //nolint:testpackage // needs access to unexported parseDuration
-
-import (
-	"testing"
-	"time"
-
-	"github.com/stretchr/testify/assert"
-	"github.com/stretchr/testify/require"
-)
-
-type parseDurationCase struct {
-	name     string
-	input    string
-	expected time.Duration
-	wantErr  bool
-}
-
-// runParseDurationCases executes a table of parseDuration cases as
-// parallel subtests.
-func runParseDurationCases(t *testing.T, tests []parseDurationCase) {
-	t.Helper()
-
-	for _, tt := range tests {
-		t.Run(tt.name, func(t *testing.T) {
-			t.Parallel()
-
-			got, err := parseDuration(tt.input)
-
-			if tt.wantErr {
-				require.Error(t, err, "expected error for input %q", tt.input)
-
-				return
-			}
-
-			require.NoError(t, err, "unexpected error for input %q", tt.input)
-			assert.Equal(t, tt.expected, got, "duration mismatch for input %q", tt.input)
-		})
-	}
-}
-
-func TestParseDurationStandard(t *testing.T) {
-	t.Parallel()
-
-	runParseDurationCases(t, []parseDurationCase{
-		{
-			name:     "standard seconds",
-			input:    "30s",
-			expected: 30 * time.Second,
-		},
-		{
-			name:     "standard minutes",
-			input:    "45m",
-			expected: 45 * time.Minute,
-		},
-		{
-			name:     "standard hours",
-			input:    "2h",
-			expected: 2 * time.Hour,
-		},
-		{
-			name:     "standard combined",
-			input:    "3h30m",
-			expected: 3*time.Hour + 30*time.Minute,
-		},
-		{
-			name:     "standard complex",
-			input:    "1h45m30s",
-			expected: 1*time.Hour + 45*time.Minute + 30*time.Second,
-		},
-		{
-			name:     "standard with milliseconds",
-			input:    "1s500ms",
-			expected: 1*time.Second + 500*time.Millisecond,
-		},
-	})
-}
-
-func TestParseDurationExtendedUnits(t *testing.T) {
-	t.Parallel()
-
-	runParseDurationCases(t, []parseDurationCase{
-		// Extended units - days
-		{
-			name:     "single day",
-			input:    "1d",
-			expected: 24 * time.Hour,
-		},
-		{
-			name:     "multiple days",
-			input:    "7d",
-			expected: 7 * 24 * time.Hour,
-		},
-		{
-			name:     "fractional days",
-			input:    "1.5d",
-			expected: 36 * time.Hour,
-		},
-		{
-			name:     "days spelled out",
-			input:    "3days",
-			expected: 3 * 24 * time.Hour,
-		},
-		// Extended units - weeks
-		{
-			name:     "single week",
-			input:    "1w",
-			expected: 7 * 24 * time.Hour,
-		},
-		{
-			name:     "multiple weeks",
-			input:    "4w",
-			expected: 4 * 7 * 24 * time.Hour,
-		},
-		{
-			name:     "weeks spelled out",
-			input:    "2weeks",
-			expected: 2 * 7 * 24 * time.Hour,
-		},
-		// Extended units - months
-		{
-			name:     "single month",
-			input:    "1mo",
-			expected: 30 * 24 * time.Hour,
-		},
-		{
-			name:     "multiple months",
-			input:    "6mo",
-			expected: 6 * 30 * 24 * time.Hour,
-		},
-		{
-			name:     "months spelled out",
-			input:    "3months",
-			expected: 3 * 30 * 24 * time.Hour,
-		},
-		// Extended units - years
-		{
-			name:     "single year",
-			input:    "1y",
-			expected: 365 * 24 * time.Hour,
-		},
-		{
-			name:     "multiple years",
-			input:    "2y",
-			expected: 2 * 365 * 24 * time.Hour,
-		},
-		{
-			name:     "years spelled out",
-			input:    "1year",
-			expected: 365 * 24 * time.Hour,
-		},
-	})
-}
-
-func TestParseDurationCombinedAndErrors(t *testing.T) {
-	t.Parallel()
-
-	runParseDurationCases(t, []parseDurationCase{
-		// Combined extended units
-		{
-			name:     "weeks and days",
-			input:    "2w3d",
-			expected: 2*7*24*time.Hour + 3*24*time.Hour,
-		},
-		{
-			name:     "years and months",
-			input:    "1y6mo",
-			expected: 365*24*time.Hour + 6*30*24*time.Hour,
-		},
-		{
-			name:     "days and hours",
-			input:    "1d12h",
-			expected: 24*time.Hour + 12*time.Hour,
-		},
-		{
-			name:  "complex combination",
-			input: "1y2mo3w4d5h6m7s",
-			expected: 365*24*time.Hour + 2*30*24*time.Hour +
-				3*7*24*time.Hour + 4*24*time.Hour +
-				5*time.Hour + 6*time.Minute + 7*time.Second,
-		},
-		{
-			name:     "with spaces",
-			input:    "1d 12h 30m",
-			expected: 24*time.Hour + 12*time.Hour + 30*time.Minute,
-		},
-		// Edge cases
-		{
-			name:     "zero duration",
-			input:    "0s",
-			expected: 0,
-		},
-		{
-			name:     "large duration",
-			input:    "10y",
-			expected: 10 * 365 * 24 * time.Hour,
-		},
-		// Error cases
-		{
-			name:    "empty string",
-			input:   "",
-			wantErr: true,
-		},
-		{
-			name:    "invalid format",
-			input:   "abc",
-			wantErr: true,
-		},
-		{
-			name:    "unknown unit",
-			input:   "5x",
-			wantErr: true,
-		},
-		{
-			name:    "invalid number",
-			input:   "xyzd",
-			wantErr: true,
-		},
-		{
-			name:    "negative not supported",
-			input:   "-5d",
-			wantErr: true,
-		},
-	})
-}
-
-func TestParseDurationSpecialCases(t *testing.T) {
-	t.Parallel()
-
-	// Test that standard Go durations work exactly as expected
-	standardDurations := []string{
-		"300ms",
-		"1.5h",
-		"2h45m",
-		"72h",
-		"1us",
-		"1µs",
-		"1ns",
-	}
-
-	for _, d := range standardDurations {
-		expected, err := time.ParseDuration(d)
-		require.NoError(t, err)
-
-		got, err := parseDuration(d)
-		require.NoError(t, err)
-		assert.Equal(t, expected, got, "standard duration %q should parse identically", d)
-	}
-}
-
-func TestParseDurationRealWorldExamples(t *testing.T) {
-	t.Parallel()
-
-	// Test real-world snapshot purge scenarios
-	tests := []struct {
-		description string
-		input       string
-		olderThan   time.Duration
-	}{
-		{
-			description: "keep snapshots from last 30 days",
-			input:       "30d",
-			olderThan:   30 * 24 * time.Hour,
-		},
-		{
-			description: "keep snapshots from last 6 months",
-			input:       "6mo",
-			olderThan:   6 * 30 * 24 * time.Hour,
-		},
-		{
-			description: "keep snapshots from last year",
-			input:       "1y",
-			olderThan:   365 * 24 * time.Hour,
-		},
-		{
-			description: "keep snapshots from last week and a half",
-			input:       "1w3d",
-			olderThan:   10 * 24 * time.Hour,
-		},
-		{
-			description: "keep snapshots from last 90 days",
-			input:       "90d",
-			olderThan:   90 * 24 * time.Hour,
-		},
-	}
-
-	for _, tt := range tests {
-		t.Run(tt.description, func(t *testing.T) {
-			t.Parallel()
-
-			got, err := parseDuration(tt.input)
-			require.NoError(t, err)
-			assert.Equal(t, tt.olderThan, got)
-
-			// Verify the duration makes sense for snapshot purging
-			assert.Greater(t, got, time.Hour,
-				"snapshot purge duration should be at least an hour")
-		})
-	}
-}

internal/cli/snapshot.go

@@ -141,7 +141,8 @@ specifying a path using --config or by setting VAULTIK_CONFIG to a path.`,
 			"orphaned blobs")
 	cmd.Flags().StringVar(&opts.KeepNewerThan, "keep-newer-than", "",
 		"With --prune: keep snapshots newer than this duration "+
-			"(e.g. 4w, 30d, 6mo) instead of only the latest")
+			"(e.g. 30d, 4w, 6mo, 1y; m is minutes, mo is months) "+
+			"instead of only the latest")
 
 	return cmd
 }
@@ -204,7 +205,8 @@ restrict the operation to specific snapshot names.`,
 	cmd.Flags().BoolVar(&opts.KeepLatest, "keep-latest", false,
 		"Keep only the latest snapshot of each name")
 	cmd.Flags().StringVar(&opts.OlderThan, "older-than", "",
-		"Remove snapshots older than duration (e.g., 30d, 6m, 1y)")
+		"Remove snapshots older than duration "+
+			"(e.g. 30d, 4w, 6mo, 1y; m is minutes, mo is months)")
 	cmd.Flags().BoolVar(&opts.Force, "force", false, "Skip confirmation prompt")
 	cmd.Flags().StringArrayVar(&opts.Names, "snapshot", nil,
 		"Restrict to snapshots with these names (repeat for multiple)")

internal/vaultik/helpers.go

@@ -33,8 +33,9 @@ func ubytes(n int64) string {
 var (
 	errMalformedSnapshotID = errors.New(
 		"invalid snapshot ID format: expected hostname_snapshotname_timestamp")
-	errInvalidDuration = errors.New("invalid duration")
-	errUnknownTimeUnit = errors.New("unknown time unit")
+	errInvalidDuration  = errors.New("invalid duration")
+	errUnknownTimeUnit  = errors.New("unknown time unit")
+	errNegativeDuration = errors.New("negative durations are not supported")
 )
 
 // Time-unit lengths used by parseDuration.
@@ -138,8 +139,13 @@ func parseSnapshotName(snapshotID 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 (h, m, s).
+// duration units. Following Go, m is minutes and mo is months. A bare number,
+// an unknown unit, and a negative value are all rejected.
 func parseDuration(s string) (time.Duration, error) {
+	if strings.HasPrefix(strings.TrimSpace(s), "-") {
+		return 0, errNegativeDuration
+	}
+
 	d, err := time.ParseDuration(s)
 	if err == nil {
 		return d, nil

internal/vaultik/helpers_test.go

@@ -51,13 +51,32 @@ func TestParseDuration(t *testing.T) {
 		want  time.Duration
 		err   bool
 	}{
-		{"30d", 30 * 24 * time.Hour, false},
-		{"4w", 4 * 7 * 24 * time.Hour, false},
-		{"6mo", 6 * 30 * 24 * time.Hour, false},
-		{"1y", 365 * 24 * time.Hour, false},
-		{"2w3d", 2*7*24*time.Hour + 3*24*time.Hour, false},
-		{"1h", time.Hour, false},
+		// Go units, including the m-is-minutes / mo-is-months distinction
+		// that this parser exists to keep straight.
+		{"10ns", 10 * time.Nanosecond, false},
+		{"10us", 10 * time.Microsecond, false},
+		{"500ms", 500 * time.Millisecond, false},
 		{"30s", 30 * time.Second, false},
+		{"6m", 6 * time.Minute, false},
+		{"1h", time.Hour, false},
+		// Extended calendar units.
+		{"30d", 30 * 24 * time.Hour, false},
+		{"3days", 3 * 24 * time.Hour, false},
+		{"4w", 4 * 7 * 24 * time.Hour, false},
+		{"2weeks", 2 * 7 * 24 * time.Hour, false},
+		{"6mo", 180 * 24 * time.Hour, false},
+		{"1month", 30 * 24 * time.Hour, false},
+		{"1y", 365 * 24 * time.Hour, false},
+		{"2years", 2 * 365 * 24 * time.Hour, false},
+		// Combined units.
+		{"2w3d", 2*7*24*time.Hour + 3*24*time.Hour, false},
+		{"1y6mo", 365*24*time.Hour + 180*24*time.Hour, false},
+		// Rejected inputs.
+		{"6", 0, true},   // bare number, no unit
+		{"5x", 0, true},  // unknown unit
+		{"-5d", 0, true}, // negative, extended unit
+		{"-5h", 0, true}, // negative, Go unit
+		{"", 0, true},    // empty
 		{"garbage", 0, true},
 	}