Stop secret mv deleting a secret moved onto itself (closes #73)

`secret mv --force x x` deleted the secret: a move within one vault
removes an existing destination before renaming the source onto it. The
same happened for `work:x work:`, `work:x work` and `work:x ""`, where an
empty destination defaults to the source name.

moveSecretWithinVault now rejects a move whose two names are the same
before touching anything. A move within a named vault works in that
vault directly instead of selecting it, so the current vault never
changes; the vault must be one of the existing vaults.

The test runs each rejected move on a copy of two in-memory vaults and
requires the exact error and an unchanged state directory.

Model: opus-5-5

internal/cli/move_test.go

@@ -0,0 +1,83 @@
+package cli_test
+
+import (
+	"testing"
+
+	"git.eeqj.de/sneak/secret/internal/cli"
+	"github.com/spf13/cobra"
+	"github.com/stretchr/testify/require"
+)
+
+// TestRejectedMoveWithinVaultLeavesStateUnchanged is a regression test for
+// https://git.eeqj.de/sneak/secret/issues/73, where a forced move of a secret
+// onto itself deleted it, and a failed move within "work" left "work" the
+// current vault. "default" is the current vault in every case, and each case
+// runs on its own copy of the state directory.
+//
+//nolint:paralleltest // newTwoVaultFs uses t.Setenv
+func TestRejectedMoveWithinVaultLeavesStateUnchanged(t *testing.T) {
+	before := snapshotStateDir(t, newTwoVaultFs(t))
+	require.Equal(t, "default", before[testStateDir+"/currentvault"])
+
+	const (
+		ontoItself = "secret 'x' cannot be moved onto itself"
+		workX      = "work:x"
+	)
+
+	tests := []struct {
+		command      string
+		source, dest string
+		force        bool
+		wantErr      string
+	}{
+		{"mv x x", "x", "x", false, ontoItself},
+		{"mv --force x x", "x", "x", true, ontoItself},
+		{"mv --force work:x work:", workX, "work:", true, ontoItself},
+		// An empty destination name defaults to the source name.
+		{`mv --force work:x ""`, workX, "", true, ontoItself},
+		// "work" is a vault name, so the destination is work:x.
+		{"mv --force work:x work", workX, "work", true, ontoItself},
+		{
+			"mv work:nosuch work:y", "work:nosuch", "work:y", false,
+			"secret 'nosuch' not found",
+		},
+		// Only an existing vault is used, so ".." cannot reach the state
+		// directory itself.
+		{
+			"mv --force ..:x ..:y", "..:x", "..:y", true,
+			"vault '..' does not exist",
+		},
+	}
+
+	for _, tt := range tests {
+		t.Run(tt.command, func(t *testing.T) {
+			fs := newFsFromSnapshot(t, before)
+			c := cli.NewCLIInstanceWithStateDir(fs, testStateDir)
+
+			err := c.MoveSecret(&cobra.Command{}, tt.source, tt.dest, tt.force)
+
+			require.Equal(t, before, snapshotStateDir(t, fs))
+			require.EqualError(t, err, tt.wantErr)
+		})
+	}
+}
+
+// TestMoveWithinOtherVaultKeepsCurrentVault checks that `secret mv work:x
+// work:y`, with "default" the current vault, renames "x" to "y" in "work" and
+// leaves "default" the current vault.
+//
+//nolint:paralleltest // newTwoVaultFs uses t.Setenv
+func TestMoveWithinOtherVaultKeepsCurrentVault(t *testing.T) {
+	fs := newTwoVaultFs(t)
+	c := cli.NewCLIInstanceWithStateDir(fs, testStateDir)
+
+	err := c.MoveSecret(&cobra.Command{}, "work:x", "work:y", false)
+	require.NoError(t, err)
+
+	after := snapshotStateDir(t, fs)
+	workSecrets := testStateDir + "/vaults.d/work/secrets.d/"
+
+	require.Equal(t, "default", after[testStateDir+"/currentvault"])
+	require.Contains(t, after, workSecrets+"y/")
+	require.NotContains(t, after, workSecrets+"x/")
+}