Appending using COPY is broken for two input files

[greybaddin]

The COPY command supports appending files using the syntax

COPY file1+file2[+[...]] file1

and this does work for three input files (and more I assume) but not for two !

Although it creates the correct output file for more than two input files the output to console is incorrect as the second file is shown as copied not appended.

[PerditionC]

COPY file1 + file2 +... file1
seems to have some varying semantics depending on shell, but generally it should (current does NOT) work successfully if file1 is first file and destination (should extend and append to existing content as long as enough room for all files, otherwise error with insufficient space message), however, if instead copying to file2 or later, then instead of creating corrupted file (as may be done) it should error as source and dest cannot be same file.