bug#9361: 24.0.50; default value of `dired-do-chmod'

[Drew Adams]

This command was better before we added a default value (in Emacs 23).
 
For one thing, the default value is a bit confusing - it uses one of the
several possible syntaxes for `chmod' - the most verbose one, which
means the most editing.
 
For another thing, the default value comes from the current permissions
of the first file that is marked.  Privileging that file makes little or
no sense when there are multiple files marked.  A better value would
come from the _minimum_ permissions for each of u, g, o, among all the
files marked.  A different argument could be made that the permissions
of the current line should be used - to apply them without editing to
all of the marked files.
 
But even with such possible changes, I think it's a bad idea to provide
any default for this command.
 
For a third thing, if someone picks up that default value then more
editing is required than just starting from nothing.  It is a lot easier
to type `g-w' than it is to back up the right number of chars and edit
the `g=rw' (or whatever the current `g' permissions are) part of the
default value, to get the proper new absolute permissions value for `g'.
 
For a fourth thing, if the permissions are currently the same (for the
first file, which is privileged here), then `a=rw' (or whatever the
current permissions are) is a better default than `u=rw, g=rw, o=rw'.
For one thing it is quicker to read and manipulate.  For another, it
teaches users that they can use `a' as a shortcut.
 
The best approach is not to provide any default value here.  A user of
this Emacs command needs to know UNIX `chmod' anyway, and if known then
it is not hard to type the permissions from scratch.
 
If you really want to improve this, then let, say, `?' give some short
help about `chmod' - e.g. present an example.  But a default value is
not helpful here.
 

In GNU Emacs 24.0.50.1 (i386-mingw-nt5.1.2600)
 of 2011-08-22 on 3249CTO
Windowing system distributor `Microsoft Corp.', version 5.1.2600
configured using `configure --with-gcc (4.5) --no-opt'