GNU bug report logs - #15738
cp: "cp -a A B" doesn't reliably create 'B' as copy of A

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Message #5 received at submit <at> debbugs.gnu.org (full text, mbox):

From: Linda Walsh <coreutils <at> tlinx.org>
To: bug-coreutils <at> gnu.org
Subject: Inconsistency & bug cp -a A B doesn't reliably create 'B' as a copy
 of 'A' even w/--remove-destination
Date: Sun, 27 Oct 2013 12:23:48 -0700

with "--remove-destination", I think this a bug.  W/o it, it is
inconsistent with the requirement not to use "dirname/." to refer to
contents in 'rm'.

details:
	mkdir a
	touch a/file
	mkdir a/dir
	cp -a a b	#'ok'
	touch a/file2

now:
	cp -au a b	
(or)
	cp -a a b

Either form creates another complete copy of 'a' in directory 'b'.
(Note, this is historical behavior).

FWIW,
     cp -a a/ b/
behaves the same way.

However,
	cp -a a/. b/.
fails the 1st time, but not if 'b' is already created (by using a form
from above).

Technically, though, the above should fail, as it says
says to copy the dir-entry for '.' over the dot entry
in 'b'.

While using '.' as a shorthand for contents of a dir has been
normal, it no longer works in utils like 'rm'.

---!!!---

*More troublesome* is that:

	cp -a --remove-destination a b

doesn't work, but duplicates the behaviors of the above.

If 'b' is removed *before* the copy, as is documented,
then it should be no different than the case where 'a' is
copied to a non-existent 'b'.

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