test(get): secret data

testdata/get__secret__err__with__binary_run.ct

@@ -0,0 +1,16 @@
+$ fecho cmd echo hello world
+$ pda set a --secret < cmd
+$ pda get a --include-binary --run --> FAIL
+Error: "a" is marked secret; re-run with --secret to display it
+Usage:
+  pda get KEY[@DB] [flags]
+
+Aliases:
+  get, g
+
+Flags:
+  -h, --help             help for get
+  -b, --include-binary   include binary data in text output
+      --no-template      directly output template syntax
+  -c, --run              execute the result as a shell command
+      --secret           display values marked as secret