tail: let -f --retry wait for inaccessible files

The --retry option is indeed useful for both following modes
by name and by file descriptor.  The difference is that in the
latter case, it is effective only during the initial open.

As a regression of the implementation of the inotify support,
tail -f --retry would immediately exit if the given file is
inaccessible.

* src/tail.c (usage): Change the description of the --retry option:
remove the note that this option would mainly be useful when
following by name.
(main): Change diagnosing dubios uses of --retry option:
when the --retry option is used without following, then issue
a warning that this option is ignored; when it is used together
with --follow=descriptor, then issue a warning that it is only
effective for the initial open.
Disable inotify also in the case when the initial open in tail_file()
failed (which is the actual bug fix).
* init.cfg (retry_delay_): Pass excess arguments to the test function.
* tests/tail-2/retry.sh: Add new tests.
* tests/local.mk (all_tests): Mention it.
* doc/coreutils.texi (tail invocation): Enhance the documentation
of the --retry option.  Clarify the difference in tail's behavior
regarding the --retry option when combined with the following modes
name versus descriptor.
* NEWS (Bug fixes): Mention the fix.

Reported by Noel Morrison in:
http://lists.gnu.org/archive/html/coreutils/2013-04/msg00003.html

1 files changed, 11 insertions, 3 deletions

diff --git a/doc/coreutils.texi b/doc/coreutils.texi
index 92917f17f..f6f2eb4f2 100644
--- a/doc/coreutils.texi
+++ b/doc/coreutils.texi
@@ -3155,9 +3155,17 @@ will keep trying until it becomes accessible again.
 
 @item --retry
 @opindex --retry
-This option is useful mainly when following by name (i.e., with
-@option{--follow=name}).
-Without this option, when tail encounters a file that doesn't
+Indefinitely try to open the specified file.
+This option is useful mainly when following (and otherwise issues a warning).
+
+When following by file descriptor (i.e., with @option{--follow=descriptor}),
+this option only affects the initial open of the file, as after a successful
+open, @command{tail} will start following the file descriptor.
+
+When following by name (i.e., with @option{--follow=name}), @command{tail}
+infinitely retries to re-open the given files until killed.
+
+Without this option, when @command{tail} encounters a file that doesn't
 exist or is otherwise inaccessible, it reports that fact and
 never checks it again.