[OE-core] automatic recipe upgrades - making them better and sweeter

[Alexander Kanavin]

Hello,

I've been asked by RP to look into making automatic package upgrades 
work better, so here's what I'd like to improve:

1) when using 'devtool upgrade', remove the need to specify version and 
source revision on the command line, if we want to upgrade to the latest 
release. There is now distrodata/checkpkg code in place to determine 
both, so 'devtool upgrade <recipe>' could simply default to that.

2) help with LICENSE checksum changes a bit more; both devtool and AUH 
have some code for this, so I want to review what they do, and 
consolidate it in a single place. Maintainers should be able to see a 
diff of what the changes are.

3) 'devtool finish' currently does not handle the recipe upgrade 
situation well: the new recipe and patches are placed side by side with 
the current recipe. The old stuff should be removed, and a tentative 
commit should be created. So maybe add a 'devtool finish-upgrade'.

4) AUH should be stripped to its core business: sending useful emails to 
maintainers, and leave the rest to devtool. If 'devtool upgrade' 
succeeded, then corresponding patches should be attached, otherwise (if 
patch rebase failed, or a fetch issue), at least it could tell what 
happened and suggest a devtool upgrade command to get started. Any 
duplicate functionality for upgrading (stuff that is also in devtool) 
should be removed.

Anything I missed? Comments?

Thanks,
Alex