test-lib.sh: set prerequisite SANITY by testing what we really need

What we wanted out of the SANITY precondition is that the filesystem
behaves sensibly with permission bits settings.

- You should not be able to remove a file in a read-only directory,

- You should not be able to tell if a file in a directory exists if
the directory lacks read or execute permission bits.

We used to cheat by approximating that condition with "is the /
writable?" test and/or "are we running as root?" test.  Neither test
is sufficient or appropriate in environments like Cygwin.

Signed-off-by: Torsten Bögershausen <tboegi@web.de>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

diff --git a/t/test-lib.sh b/t/test-lib.sh
index b2b2ec7f1cff4462c1e7184c3e00d054efec1d58..446d8d5a1da02587fc4e21d4eb276e848a87333c 100644 (file)
--- a/t/test-lib.sh
+++ b/t/test-lib.sh
@@ -997,9 +997,28 @@ test_lazy_prereq NOT_ROOT '
        test "$uid" != 0
 '
 
-# When the tests are run as root, permission tests will report that
-# things are writable when they shouldn't be.
-test -w / || test_set_prereq SANITY
+# On a filesystem that lacks SANITY, a file can be deleted even if
+# the containing directory doesn't have write permissions, or a file
+# can be accessed even if the containing directory doesn't have read
+# or execute permissions, causing our tests that validate that Git
+# works sensibly in such situations.
+test_lazy_prereq SANITY '
+       mkdir SANETESTD.1 SANETESTD.2 &&
+
+       chmod +w SANETESTD.1 SANETESTD.2 &&
+       >SANETESTD.1/x 2>SANETESTD.2/x &&
+       chmod -w SANETESTD.1 &&
+       chmod -rx SANETESTD.2 ||
+       error "bug in test sript: cannot prepare SANETESTD"
+
+       ! rm SANETESTD.1/x && ! test -f SANETESTD.2/x
+       status=$?
+
+       chmod +rwx SANETESTD.1 SANETESTD.2 &&
+       rm -rf SANETESTD.1 SANETESTD.2 ||
+       error "bug in test sript: cannot clean SANETESTD"
+       return $status
+'
 
 GIT_UNZIP=${GIT_UNZIP:-unzip}
 test_lazy_prereq UNZIP '