[FS#826] Better implementation of upgrade system on lede

[LEDE Bugs]

The following task has a new comment added:

FS#826 - Better implementation of upgrade system on lede
User who did this - piotr (pietia)

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Hi Aparcar,
Isn't this kinda an overkill ? 
I see potentatial problem first is that every compilation won't be tested by everyone because some person might be using package A but not package B and people with package B will get unstable image and people with package A will not and it will be future hard to troubleshoot the error (we already have 500 diffrent routers that are supported by lede and I can assume it's a pain).

Using my approach can be coded in hour I'm not sure only where can we add to install packages from file post sysupgrade, except generating that big json file with 500 routers this can take hours .(but every release we just replace all  in links 17.0.1 for example for 17.0.2 and if all paths are same it will be one minute work.)

Perhaps there is some conf that stores openwrt-kirkwood-linksys-viper-squashfs instead of board.json:             "id": "linksys-viper" 
would be easier to write that json file for 500 routers.
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More information can be found at the following URL:
https://bugs.lede-project.org/index.php?do=details&task_id=826#comment2757