bug#20849: documentation: difference between empty and non-empty dirs with "mv --no-target-directory"

[Alexey Salmin]

In the steps-to-reproduce below:
- the first sequence of commands demonstrates case (B) - Non-empty directory
- the second sequence of commands is for the case (A) - Empty directory
- the third sequence is correctly labeled as (C) - File

Very sorry for the confusion.

Alexey

On Fri, Jun 19, 2015 at 4:23 PM, Alexey Salmin <address@hidden> wrote:
> Image you need to move the "$PWD/tmploc/a" directory into "$PWD/a" and
> ensure you don't end up with "$PWD/a/a" when "$PWD/a" already exists.
> The "mv --no-target-directory" (or "mv -T") does exactly that, however
> there are three different cases depending on a type of "$PWD/a":
>
> A) Empty directory: mv silently overwrites "$PWD/a" with "$PWD/tmploc/a"
> B) Non-empty directory: mv fails with a "File exists" message
> C) File: mv fails with a "cannot overwrite non-directory ... with
> directory" message
> See steps to reproduce at the bottom of this e-mail.
>
> I can see a reasoning behind this behavior and don't challenge it.
> However I would appreciate if it was clearly stated in the
> documentation.
>
> At the moment it explains "-T" as "Do not treat the last operand
> specially when it is a directory or a symbolic link to a directory."
> [1] This sort of contradicts the fact that an empty directory (A) is
> treated specially compared to an empty file (C). And a difference
> between (A) and (B) is not mentioned at all.
>
> Thank you,
> Alexey
>
>
> [1] http://www.gnu.org/software/coreutils/manual/coreutils.html#mv-invocation
>
> Steps to reproduce:
> A) Empty directory: mv silently overwrites "$PWD/a" with "$PWD/tmploc/a"
> $ find * -printf "%y %p\n"
> d a
> f a/otherfile
> d tmploc
> d tmploc/a
> f tmploc/a/file
> $ mv --no-target-directory tmploc/a a; echo $?
> mv: cannot move 'tmploc/a' to 'a': File exists
> 1
>
> B) Non-empty directory: mv fails with a "File exists" message
> $ rm a/otherfile
> $ mv --no-target-directory tmploc/a a; echo $?
> 0
> $ find * -printf "%y %p\n"
> d a
> f a/file
> d tmploc
>
> C) File: mv fails with a "cannot overwrite non-directory ... with
> directory" message
> $ find * -printf "%y %p\n"
> f a
> d tmploc
> d tmploc/a
> f tmploc/a/file
> $ mv --no-target-directory tmploc/a a; echo $?
> mv: cannot overwrite non-directory 'a' with directory 'tmploc/a'
> 1