retain old file's permissions in wrap_print()

wrap_print() was written to create a new file and rename the old one to
avoid a partially written file being read by other processes.  This has
only been reported for the 'projects.list' file, but I just did it for
all files as a matter of course.

list of files currently written via this function:
gl-creater, gl-perms, description, git-daemon-export-ok, projects.list

However, some people want to do the following:

  - set REPO_UMASK tight (0077, default)
  - manually change the perms to something looser (typically g+rX) for
    specific repos
  - set core.sharedRepository to 0750 (git is documented to honor that
    config if available and to override umask)

Except that core.sharedRepository does not apply to files written by
gitolite and not git itself.  So they would open up their description
files and the next compile would close them again!

This patch prevents this from happening.  If the file already exists, it
maintains the same permissions after the rename.

src/gitolite.pm

@@ -110,7 +110,9 @@ sub wrap_print {
     my $fh = wrap_open(">", "$file.$$");
     print $fh @text;
     close($fh) or die "$ABRT close $file failed: $! at ", (caller)[1], " line ", (caller)[2], "\n";
+    my $oldmode = ( (stat $file)[2] );
     rename "$file.$$", $file;
+    chmod $oldmode, $file if $oldmode;
 }
 
 sub slurp {