Give each failure one error value (closes #113)

internal/cli's copies of vault.ErrSecretNotFound, ErrVaultNotFound,
ErrVersionNotFound and ErrSecretExists are removed; the commands wrap the
vault errors. Every error of secret.ReadPassphrase wraps
ErrPassphraseNotRead, so its callers no longer add those words.
ResolveGPGKeyFingerprint returns ErrGPGKeyNotFound for a key the keyring
lacks, recognised by gpg's status line. storeInKeychain returns
errNilDataBuffer. bip85's ErrPasswordTooShort and ErrEncodedTooShort go
with their unreachable checks. Tests that matched these errors' text use
errors.Is.

Model: opus-5-5

internal/cli/move_test.go

@@ -45,15 +45,6 @@ func TestRejectedMoveWithinVaultLeavesStateUnchanged(t *testing.T) {
 		{`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.
-		{
-			"mv --force nosuch:x nosuch:y", "nosuch:x", "nosuch:y", true,
-			"vault 'nosuch' does not exist",
-		},
 	}
 
 	for _, tt := range tests {
@@ -70,6 +61,20 @@ func TestRejectedMoveWithinVaultLeavesStateUnchanged(t *testing.T) {
 		})
 	}
 
+	// A missing secret, and a missing vault: only an existing vault is used.
+	for source, want := range map[string]error{
+		"work:nosuch": vault.ErrSecretNotFound,
+		"nosuch:x":    vault.ErrVaultNotFound,
+	} {
+		t.Run("mv --force "+source+" work:y", func(t *testing.T) {
+			t.Parallel()
+
+			requireRejectedAndUnchanged(t, before, want, func(c *cli.Instance) error {
+				return c.MoveSecret(&cobra.Command{}, source, "work:y", true)
+			})
+		})
+	}
+
 	// Each of these spells "work" a second way. The spelling is not a valid
 	// vault name, so the move is not taken for a move between two vaults,
 	// which would delete the destination, here the source.