new feature: rm accepts new option: --one-file-system

Suggested by Steve McIntyre in <http://bugs.debian.org/392925>.
* src/remove.h (struct rm_options) [one_file_system]: New member.
* src/rm.c (rm_option_init): Initialize it.
(usage): Document the option.
* src/mv.c (rm_option_init): Likewise.
* src/remove.c (remove_dir): With --one-file-system and --recursive,
for each directory command line argument, do not affect a file system
different from that of the starting directory.  And give a diagnostic.
* src/rm.c (ONE_FILE_SYSTEM): New enum.
(main): Handle new option.
* tests/rm/one-file-system: Test the above.
* tests/rm/Makefile.am (TESTS): Add one-file-system.
* tests/Makefile.am (check-root): Add the rm/one-file-system
test to the list.
(EXTRA_DIST): Add other-fs-tmpdir.

* tests/mv/setup: Removed.  Renamed to...
* tests/other-fs-tmpdir: ...this new file.
* tests/mv/Makefile.am (EXTRA_DIST): Remove setup.
* tests/mv/acl: Reflect renaming: use ../other-fs-tmpdir.
* tests/mv/backup-is-src: Likewise.
* tests/mv/hard-link-1: Likewise.
* tests/mv/leak-fd: Likewise.
* tests/mv/mv-special-1: Likewise.
* tests/mv/part-fail: Likewise.
* tests/mv/part-hardlink: Likewise.
* tests/mv/part-rename: Likewise.
* tests/mv/part-symlink: Likewise.
* tests/mv/partition-perm: Likewise.
* tests/mv/to-symlink: Likewise.
* tests/mv/into-self-2: Likewise.

[doc/ChangeLog]
* coreutils.texi (rm invocation): Describe --one-file-system.

1 files changed, 18 insertions, 0 deletions

diff --git a/doc/coreutils.texi b/doc/coreutils.texi
index 3a180f669..ee8179246 100644
--- a/doc/coreutils.texi
+++ b/doc/coreutils.texi
@@ -7772,6 +7772,24 @@ removal is requested.  Equivalent to @option{-I}.
 Specifying @option{--interactive} and no @var{when} is equivalent to
 @option{--interactive=always}.
 
+@itemx --one-file-system
+@opindex --one-file-system
+@cindex one file system, restricting @command{rm} to
+When removing a hierarchy recursively, skip any directory that is on a
+file system different from that of the corresponding command line argument.
+
+This option is useful when removing a build ``chroot'' hierarchy,
+which normally contains no valuable data.  However, it is not uncommon
+to bind-mount @file{/home} into such a hierarchy, to make it easier to
+use one's start-up file.  The catch is that it's easy to forget to
+unmount @file{/home}.  Then, when you use @command{rm -rf} to remove
+your normally throw-away chroot, that command will remove everything
+under @file{/home}, too.
+Use the @option{--one-file-system} option, and it will
+warn about and skip directories on other file systems.
+Of course, this will not save your @file{/home} if it and your
+chroot happen to be on the same file system.
+
 @itemx --preserve-root
 @opindex --preserve-root
 @cindex root directory, disallow recursive destruction