tilde expansion failure

[<bma...@we...>]

Currently tilde expansion of paths like "~/gnuplot.history" via gp_expand_tilde() 
on Windows 9x will fail unless the user sets the HOME environment variable.
The string containing the path is left unchanged and does therefore not contain
a valid path. 

This problem came up while I was working on the GNUPLOT_HISTORY patch (see SF).
It applies to locating wgnuplot.ini as well as tilde expansion in "load/save" commands.
I could think of different solutions:

1) Issue a warning that a certain functionality (e.g. saving of history) of gnuplot 
requires HOME to be set and do nothing if it is not. (I.e. don't load/save history.)

2) Use a default directory instead, where 'default' could be the current
directory or the directory where gnuplot.exe resides. The first being more
reasonable for "load/save" commands and the later for locating the history
file and wgnuplot.ini.

3) Use a completely different approach to locate files on Windows and disable
tilde expansion there as most users of that platform don't know that 
concept anyway. (No, this would not introduce a lot of #ifdefs. Only
gp_expand_tilde would have to be modfied.

What would be a good solution?


Bastian