what is the right exit code for some vanished files?

[Matt McCutchen]

On Sun, 2007-12-16 at 13:47 -0500, Ming Zhang wrote:
> > even code 24 is in order because the nonexistence of a --files-from
> > entry cannot affect the correctness of a run with --delete in the way
> > that a traditional vanishing can.
> 
> not quite understand what u meant here...

Sorry.  I was thinking of this comment:

https://bugzilla.samba.org/show_bug.cgi?id=3653#c11

To elaborate:

Rsync generally satisfies the following correctness property: at the end
of a successful run with no concurrent modification of the destination,
every aspect of the destination that is within the scope of the run (as
determined by the file-list and options) reflects a state that the
corresponding aspect of the source had at some time during the run.

Suppose files src/A and dest/A differ.  Suppose we run "rsync -a
--delete src/ dest/" and delete src/A during the run.  To satisfy the
property, rsync should either delete dest/A or fill it with the
pre-deletion contents of src/A.  However, if src/A vanishes after it is
added to the file-list but before the sender can transfer it, rsync
reports src/A as vanished and leaves dest/A alone, violating the
correctness property.  I believe that the code 24 is needed to warn the
user that correctness may have been violated in this way.

On the other hand, if src/A vanishes before it is added to the file-list
(as in the inotify case), rsync deletes dest/A from the destination, so
the run satisfies the correctness property.  Then the only issue is
whether to alert the user that s/he may have mistyped the --files-from
entry.  By default, rsync alerts the user with a code 23.  In the case
of inotify, an option would indicate that this alerting is not desired,
and no exit code would be needed at all.

Matt