The magic.mgc file gets created in the local directory, opening
the global file throws unwanted messages. So we are using the o/p
of the file command to determine if the file is a plain text file.

Use mpv, fmedia, zathura.
Invoke libmagic to identify text files and open with vim.
Use xdg-open for unhandled mimes.

NetBSD has its own curses implementation and initscr() does not
terminate with an error if TERM is not set properly.

Instead check the return value and exit if an initialization
error occurs.

Original patch written by Richard Hyde and taken from
https://github.com/RichardHyde/noice

Patch written by Richard Hyde and taken from
https://github.com/RichardHyde/noice

It should be the size of the destination buffer, not the source.

In this case, both src and dest have the same size.

This is more descriptive for a global variable which
can easily be shadowed.

Nobody uses it and adds additional complexity.

The code was quite fragile.  As a first pass, use buffers of size
PATH_MAX and LINE_MAX accordingly until we simplify the overall logic.

Avoids weird things like /etc/.. when displaying cwd.

Also no need for cwd to be on the heap.

Specifying commands by name in config.h means that
every time one switches ones editor (for example),
one has to modify every config.h file referencing that editor
and then recompile every corresponding program.

This change adds a string `env` for specifying an environment
variable to `struct key` and uses it to optionally specify the
command to run on SEL_{RUN,RUNARG}.
The `run` string is used as a fallback when the environment variable
has not been specified or is not set.
It also updates `config.def.h` to demonstrate this new capability.

Thanks Hiltjo!