Make NanoBSD source-able from other scripts.

[will]

Summary

This change converts NanoBSD into a two-script bundle.

• defaults.sh contains all non-CLI code. Most NanoBSD code is moved into this file.
• nanobsd.sh now consists just of a command line interface that calls into functions in defaults.sh.

Test Plan

Run NanoBSD using a previously-working configuration.

[imp]

So what's the motivation for this?

tools/tools/nanobsd/nanobsd.sh

32 ↗

(On Diff #2755)

Does this work if you've run the shell script via a path listed in $PATH?

[will]

The motivation is primarily to enable using NanoBSD within another script. This can be useful for sharing configuration data, for example.

[imp]

Sure, but there's one big caveat. The API between nanobsd.sh and defaults.sh is currently undocumented and subject to change. cust_pkg is definitely going to be deleted soon, for example. All the geometry stuff to create a disk is likely to be redone (though the current APIs might remain).

Unless there's documentation and/or documented users, external folks are going to have a bumpy ride.

[will]

That's true, but the point of the change is merely to enable reuse, not necessarily to make any sort of API guarantee.

tools/tools/nanobsd/nanobsd.sh

32 ↗

(On Diff #2755)

Yes; as far as I can tell, this mechanism works regardless of how you invoke the script. In that particular case, $0 is already the fully expanded path:

will@sol% cat ~/bin/foo; foo
#!/bin/sh
x=realpath $0
echo "\$0='$0' x='${x}'"
$0='/home/will/bin/foo' x='/home/will/bin/foo'
will@sol% cd ~/bin; ./foo
$0='./foo' x='/home/will/bin/foo'

[will]

Closed by commit rS275832 (authored by @will).