firefox-wrapper: start firefox (a workaround for some $PATH nonsense).

edit-clipboard: open current contents of clipboard in $EDITOR, write them
back to clipboard.  relies on xclip.

mcd(): a function to make a path and cd into it.

These were missing a `%`.

This should be slightly more correct and doesn't result in an extra blank
line.

See: https://p1k3.com/2016/7/11/ - "extracting all (?) of the filenames
from packages available in debian"

Amends last commit by tacking on current changes.

The main thing here is that alt-[arrow] will work for jumping windows.

Does, for the moment, nothing.  Probably will never do anything.  But then
you never know.

Uses comm(1) and bash process substitution to show filenames common between
two directories.

For use with the new mark(1) I've been sketching out lately.

I kept hitting backspace and winding up on the wrong wiki page.

I think I've finally reached the point where swapfiles have cost me more
time and effort than they've saved me.

From https://github.com/brennen/snowday

I was hoping to _just_ get rid of the shortening of long URLs, but as it
happens this affects other stuff (links, etc.) that's much more annoying.

Useful for figuring out what $PATH things run in the window manager
environment but not from within a shell can see.