rm: disallow --n alias for --no-preserve-root

* src/rm.c (main): Ensure the full --no-preserve-root
option is specified, rather than allowing --n etc.
* tests/rm/r-root.sh: Add a test case.
* NEWS: Mention the change in behavior.

Improved by Jim Meyering.
Fixes http://bugs.gnu.org/24604

3 files changed, 16 insertions, 2 deletions

diff --git a/NEWS b/NEWS
index c3554d0fe..e68de05a2 100644
--- a/NEWS
+++ b/NEWS
@@ -52,6 +52,8 @@ GNU coreutils NEWS                                    -*- outline -*-
 
 ** Changes in behavior
 
+  rm no longer accepts shortened variants of the --no-preserve-root option.
+
   seq no longer accepts 0 value as increment, and now also rejects NaN
   values for any argument.
 
@@ -81,8 +83,8 @@ GNU coreutils NEWS                                    -*- outline -*-
 
 ** New Features
 
-   date now accepts the --debug option, to annotate the parsed date string,
-   display timezone information, and warn about potential misuse.
+  date now accepts the --debug option, to annotate the parsed date string,
+  display timezone information, and warn about potential misuse.
 
 
 * Noteworthy changes in release 8.25 (2016-01-20) [stable]
diff --git a/src/rm.c b/src/rm.c
index 13a5714c3..2c54405f7 100644
--- a/src/rm.c
+++ b/src/rm.c
@@ -287,6 +287,9 @@ main (int argc, char **argv)
           break;
 
         case NO_PRESERVE_ROOT:
+          if (! STREQ (argv[optind - 1], "--no-preserve-root"))
+            error (EXIT_FAILURE, 0,
+                   _("you may not abbreviate the --no-preserve-root option"));
           preserve_root = false;
           break;
 
diff --git a/tests/rm/r-root.sh b/tests/rm/r-root.sh
index b98db141b..3b7837fe0 100755
--- a/tests/rm/r-root.sh
+++ b/tests/rm/r-root.sh
@@ -211,6 +211,15 @@ for opts in           \
 done
 
 #-------------------------------------------------------------------------------
+# Exercise with --no-preserve to ensure shortened equivalent is not allowed.
+cat <<EOD > exp_opt || framework_failure_
+rm: you may not abbreviate the --no-preserve-root option
+EOD
+returns_ 1 exercise_rm_r_root --no-preserve / || fail=1
+compare exp_opt err || fail=1
+test -f x && fail=1
+
+#-------------------------------------------------------------------------------
 # Exercise "rm -r file1 / file2".
 # Expect a non-Zero exit status representing failure to remove "/",
 # yet 'file1' and 'file2' should be removed.