echo: special case "echo --help": it should not show help text

While at it, fix "busybox --help echo" and other special applets to still print
the help text.

function                                             old     new   delta
run_applet_and_exit                                  732     761     +29
show_usage_if_dash_dash_help                          70      78      +8
------------------------------------------------------------------------------
(add/remove: 0/0 grow/shrink: 2/0 up/down: 37/0)               Total: 37 bytes

Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>

1 files changed, 22 insertions, 8 deletions

diff --git a/libbb/appletlib.c b/libbb/appletlib.c
index 67c540abb..2feed64dd 100644
--- a/libbb/appletlib.c
+++ b/libbb/appletlib.c
@@ -263,9 +263,14 @@ void lbb_prepare(const char *applet
          && strcmp(argv[1], "--help") == 0
          && !is_prefixed_with(applet, "busybox")
         ) {
-                /* Special case. POSIX says "test --help"
-                 * should be no different from e.g. "test --foo".  */
-                if (!ENABLE_TEST || strcmp(applet_name, "test") != 0)
+                /* Special cases. POSIX says "test --help"
+                 * should be no different from e.g. "test --foo".
+                 */
+                if (!(ENABLE_TEST && strcmp(applet_name, "test") == 0)
+                 && !(ENABLE_TRUE && strcmp(applet_name, "true") == 0)
+                 && !(ENABLE_FALSE && strcmp(applet_name, "false") == 0)
+                 && !(ENABLE_ECHO && strcmp(applet_name, "echo") == 0)
+                )
                         bb_show_usage();
         }
 #endif
@@ -891,15 +896,21 @@ int busybox_main(int argc UNUSED_PARAM, char **argv)
                 if (!argv[2])
                         goto help;
                 /* convert to "<applet> --help" */
-                argv[0] = argv[2];
+                applet_name = argv[0] = argv[2];
                 argv[2] = NULL;
+                if (find_applet_by_name(applet_name) >= 0) {
+                        /* Make "--help foo" exit with 0: */
+                        xfunc_error_retval = 0;
+                        bb_show_usage();
+                } /* else: unknown applet, fall through (causes "applet not found" later) */
         } else {
                 /* "busybox <applet> arg1 arg2 ..." */
                 argv++;
+                /* We support "busybox /a/path/to/applet args..." too. Allows for
+                 * "#!/bin/busybox"-style wrappers
+                 */
+                applet_name = bb_get_last_path_component_nostrip(argv[0]);
         }
-        /* We support "busybox /a/path/to/applet args..." too. Allows for
-         * "#!/bin/busybox"-style wrappers */
-        applet_name = bb_get_last_path_component_nostrip(argv[0]);
         run_applet_and_exit(applet_name, argv);
 }
 # endif
@@ -910,7 +921,7 @@ void FAST_FUNC show_usage_if_dash_dash_help(int applet_no, char **argv)
         /* Special case. POSIX says "test --help"
          * should be no different from e.g. "test --foo".
          * Thus for "test", we skip --help check.
-         * "true" and "false" are also special.
+         * "true", "false", "echo" are also special.
          */
         if (1
 #  if defined APPLET_NO_test
@@ -922,6 +933,9 @@ void FAST_FUNC show_usage_if_dash_dash_help(int applet_no, char **argv)
 #  if defined APPLET_NO_false
          && applet_no != APPLET_NO_false
 #  endif
+#  if defined APPLET_NO_echo
+         && applet_no != APPLET_NO_echo
+#  endif
         ) {
                 if (argv[1] && !argv[2] && strcmp(argv[1], "--help") == 0) {
                         /* Make "foo --help" exit with 0: */