[glean-dev] --overwrite option

[Brian P. <bri...@tu...>]

When debugging test failures I typically need to run the same glean 
test over and over.  Each time, I either have to provide a new results 
directory, or remove the previous one.  Otherwise, glean refuses to 
run/overwrite an existing results directory/file.  This is pretty 
inconvenient when you're in gdb.

The attached patch adds a -o/--overwrite option that'll erase the 
named results database if it exists.

I'm not sure it's the right approach though.  The other approach would 
be to do --run without naming a results directory (no results would be 
logged).  But it looks a little harder to implement that.  Can we 
create a /dev/null-like output stream?  That might make it easy.

Comments?

-Brian