This one is a bit shaky still, but I now have symbolic,
colour-coded tags in the prompt. This can be used to point out
interesting lines in pair programming.
I removed the need for the ~/.tcsh_cache directory. The right-side
alignment is handled with terminal control codes. I stick
exclusively to ANSI/VT-100 control codes. Everything should support
that by now, it's 2021!
In generating CSHENV prompts, I used stty(1) to find the width
of the current terminal, at sourcing time. SYSV and BSD use
different output formats. Presently I have tcshrc.prompt.defs
default to 80 columns when I don't know how to parse stty(1)'s
output. AIX is known to be a SYSV variant, and I've added a
case to handle this.
I didn't test the script on a virgin system, until I did it on a new
cygwin system. Now I have discovered this, and I have fixed it to properly
create the cache dir again.