bug#36831: Enhance directory move. (was Re: bug#36831: enhance 'directory not empty' message)

[Assaf Gordon]

Hello,

On Fri, Aug 02, 2019 at 02:41:31AM -0700, L A Walsh wrote:
> On 2019/07/28 23:28, Assaf Gordon wrote:
> >
> >
> >     $ mkdir A B B/A
> >     $ touch A/bar B/A/foo
> >     $ mv A B
> >     mv: cannot move 'A' to 'B/A': Directory not empty
> >
> > And the reason (as you've found out) is that the target directory 'B/A'
> > is not empty (has the 'foo' file in it).
> > Had this been allowed, moving 'A' to 'B/A' would result in the 'foo'
> > file disappearing.
> >   
> ---
>     Why must foo disappear?
> 
>     Microsoft Windows handles this situation by telling the user that
> the target directory already exists and giving the option to *MERGE*
> the directories.
> 
>     If you attempt to move a file into a directory that already contains
> a file by the same name, it pops up another notice asking [...]

Certainly, GUI programs (and more 'feature-rich' programs than 'mv')
offer many "merging" options.

I'm sure Midnight-Commander, KDE/Doplhine, XFCE/Thunar, Gnome/Nautilus
and many other free software GUI file managers have some "merging"
capabilities.

But 'mv' is more basic and does not have this capability.
Partly that is because it adheres to the POSIX standards, which
mandates:
    "3. The mv utility shall perform actions equivalent to the
        rename() function [...]"
https://pubs.opengroup.org/onlinepubs/9699919799/utilities/mv.html

Some rsync options (--remove-source-files) can mimick 'mv' with merging,
but then they are more like "copy+delete" than actual "rename/move".


Can new merging features be added to 'mv'? yes.
But it seems to me these would be better suited for 'higher level'
programs (e.g. a GUI file manager).

regards,
 - assaf