tools: add support for subkeys in release tools

[MylesBorins]

Replace grep with awk to add support for subkeys

/cc @rvagg@jasnell@Fishrock123 @nodejs/build

[MylesBorins]

I'm not 100% we want to be using the -E flag here. Personally I don't see a problem, but perhaps we want to solve this without using an extended regular expression

[Fishrock123]

As a note, my subkey works, but it always prints the "GPG key for \"${version}\" tag is not yours, cannot sign" error. (Because something detects my master key instead, and git ends up signing with a subkey. (I think?))

[MylesBorins]

Any thoughts on this @rvagg ?

[rvagg]

Yeah, this works, I was working up a complicated solution in my head but the fact that this simply prompts you to choose makes it a simple fix! Good thinking.

grep '^sec\|^ssb' works without the -E but we may as well just roll it up into the awk with:

gpgkey=$(gpg --list-secret-keys | awk -F'( +|/)' '/^(sec|ssb)/{print $3}') 

lgtm with that change.

[MylesBorins]

@rvagg I added the change and rebased against master

[rvagg]

lgtm, I think you can probably land this at will now, thanks @thealphanerd!

[MylesBorins]

Landed in 321162d