[TCLCORE] file copy and link handling

[Jeff H. <JeffH@ActiveState.com>]

Hemang brought up the following dilemma regarding the 'file copy' command
in Tcl:

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It seems when I use "file copy -force -- $src $dst" and if $src is a
soft link, then the resultant $dst created is also a softlink. Moreover,
if $src is relative, $dst is also created as relative softlink which can
result in error if the $dst has a different path. See below:

godel:73> ls -l 
total 80
drwxr-xr-x   2 hlavana  eng           69 Jul 24 17:04 bar
lrwxrwxrwx   1 hlavana  eng            8 Jul 24 17:01 foo -> test.exp
-rw-r--r--   1 hlavana  eng           44 Jul 24 17:01 test.exp
godel:74> tclsh
% info patch
8.3.4
% file copy -force -- foo bar/abc
% exit
godel:75> ls -l bar/
total 16
lrwxrwxrwx   1 hlavana  eng            8 Jul 24 17:05 abc -> test.exp
godel:76> cat bar/abc 
cat: cannot open bar/abc
godel:77>  cp foo bar/def
godel:78> ls -l bar/def 
-rw-r--r--   1 hlavana  eng           44 Jul 24 17:08 bar/def
godel:79> 

On the other hand, if I use the unix cp command, it copies the file
instead of creating a softlink. The same behavior is also observed with
tcl8.4 (CVS Head). Is this the expected behavior?
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The question is, should Tcl be copying these as softlinks, or should
it be more intelligent about it.  Note that 8.4 file docs actually do
doc the above behavior, but that is only because we (ActiveState)
noticed this (what we considered unexpected) behavior and added it to
the 8.4 docs for others.  I don't want to necessarily validate that
as the behavior though, if everyone else doesn't expect it either.

Note that Linux has a cp -d option to copy as links, but Solaris and
HP don't.  However, cp -r on HP does copy links as links, whereas
it normally copies links into new files (it docs this).

Thoughts anyone?  I'm inclined to make it check for links and copy
those as files, but then this would slightly change behavior.  The
unix 'cp' throws an error, even with -f, when you want to copy a link
that points to a non-existent file.  Currently tcl doesn't complain
at all, because it is only copying the link itself.

  Jeff Hobbs                     The Tcl Guy
  Senior Developer               http://www.ActiveState.com/
      Tcl Support and Productivity Solutions
 Join us in Sept. for Tcl'2002: http://www.tcl.tk/community/tcl2002/