Hold the encrypt and decrypt result in memory until it is written (closes #143)

With --output, secret encrypt and secret decrypt emptied that file before
reading any input, so a failed command left it empty, and encrypting a file
onto itself gave the encryption of nothing.

With --output they now hold the result in memory and open --output, with the
same call as before, only once encryption or decryption has succeeded. A
failure to encrypt or decrypt leaves --output untouched, and --input can be the
same file. A failure while writing --output, such as a full disk, can leave it
empty or partly written; an error from closing it is reported. Without
--output the result still goes to stdout as it is produced.

Model: opus-5-5

README.md

@@ -67,6 +67,10 @@ and unlocker set. This allows for complete isolation between different contexts
 
 ## Commands Reference
 
+Every time `secret` prints, in a table or in `--json` output, is in UTC,
+whatever `TZ` or the system's time zone is set to. The date in a version's name
+is the UTC date too.
+
 ### Confirmation Before Removal
 
 `secret rm`, `secret version rm`, `secret vault remove` and
@@ -318,7 +322,7 @@ With `--output`, `secret encrypt` and `secret decrypt` hold the result in memory
 and write it to `--output` only once encryption or decryption has succeeded, so
 a failure to encrypt or decrypt leaves `--output` untouched. A failure while
 writing `--output`, such as a full disk, can leave it empty or partly written.
-The command needs about as much memory as the result.
+The command can need up to about four times as much memory as the result.
 
 #### `secret encrypt <secret-name> [--input=file] [--output=file]`
 

internal/cli/list_times_test.go

@@ -3,6 +3,9 @@ package cli_test
 import (
 	"bytes"
 	"encoding/json"
+	"os"
+	"os/exec"
+	"path/filepath"
 	"testing"
 	"time"
 
@@ -125,6 +128,57 @@ func TestMovedSecretKeepsItsTimes(t *testing.T) {
 		"updated %s, then %s", beforeMove.UpdatedAt, afterMove.UpdatedAt)
 }
 
+// TestListedTimesAreUTC is a regression test for
+// https://git.eeqj.de/sneak/secret/issues/169, where times were printed
+// in the local time zone. It runs `secret list` on the built binary with
+// TZ set to New York, where the secret's last update, 03:04:05 UTC on 2
+// January, is 22:04:05 the day before.
+func TestListedTimesAreUTC(t *testing.T) {
+	t.Parallel()
+
+	stateDir := t.TempDir()
+
+	vlt, err := vault.CreateVault(
+		afero.NewOsFs(), stateDir, "default", testMnemonicBuffer(t), nil)
+	require.NoError(t, err)
+
+	vlt.Mnemonic = testMnemonicBuffer(t)
+	err = vlt.AddSecret("x", memguard.NewBufferFromBytes([]byte("one")), false)
+	require.NoError(t, err)
+
+	updated := time.Date(2026, time.January, 2, 3, 4, 5, 0, time.UTC)
+	current := filepath.Join(stateDir, "vaults.d", "default", "secrets.d", "x",
+		"current")
+	require.NoError(t, os.Chtimes(current, updated, updated))
+
+	tests := []struct {
+		flags []string
+		want  string
+	}{
+		{flags: nil, want: "2026-01-02 03:04"},
+		{
+			flags: []string{"--json"},
+			want:  `"updated_at": "2026-01-02T03:04:05Z"`,
+		},
+	}
+
+	for _, tt := range tests {
+		args := append([]string{"list"}, tt.flags...)
+
+		//nolint:gosec // G204: test executes the freshly built secret binary
+		cmd := exec.CommandContext(t.Context(), secretBinaryPath(t), args...)
+		cmd.Env = []string{
+			secret.EnvStateDir + "=" + stateDir,
+			"TZ=America/New_York",
+			"PATH=" + os.Getenv("PATH"),
+		}
+
+		output, err := cmd.CombinedOutput()
+		require.NoError(t, err, "%v: %s", args, output)
+		assert.Contains(t, string(output), tt.want, "%v", args)
+	}
+}
+
 // listSecrets returns the output of `secret list`, or of
 // `secret list --json` when jsonOutput is set.
 func listSecrets(t *testing.T, c *cli.Instance, jsonOutput bool) string {

internal/cli/root.go

@@ -2,6 +2,7 @@ package cli
 
 import (
 	"os"
+	"time"
 
 	"github.com/awnumar/memguard"
 	"github.com/spf13/cobra"
@@ -14,6 +15,10 @@ import (
 // every memguard buffer before it returns, so the caller must do nothing
 // but exit with the code.
 func Entry() int {
+	// Every time secret prints or writes is in UTC, whatever TZ or the
+	// system's time zone is set to.
+	time.Local = time.UTC //nolint:gosmopolitan // this makes local time UTC
+
 	raiseLockedMemoryLimit()
 
 	// On SIGINT or SIGTERM memguard runs this function, wipes every buffer