[LEDE-DEV] [PATCH v2 2/4] base-files: add sysupgrade -u to skip unchanged files

[Luiz Angelo Daros de Luca]

> This patch series works very nicely for me on ar71xx, brcm47xx, ipq806x
> and lantiq, -u unclutters the overlay contents quite significantly and
> makes spotting (manual) changes a lot easier.

Thanks Stefan for the feedback. If you want to simply spot changes, I would
recommend '-o -l'.
I normally use '-o -u -k -b mybkp.tgz'.

I use backup like these for years and since last year I'm trying to share
it to everybody. It has already saved me several hours.

For those that want to keep track, I'm using this branch for it:

https://github.com/luizluca/openwrt/raw/better-backups-v2/package/base-files/files/sbin/sysupgrade

It already has some minor fixes on top of sent patches.

And for those that simply want to test it (or use it):

$ wget -O /sbin/sysupgrade.alt
https://raw.githubusercontent.com/luizluca/openwrt/better-backups-v2/package/base-files/files/sbin/sysupgrade
$ chmod +x /sbin/sysupgrade.alt

It's a shame githubusercontent.com forces https.

It is safe to use this "standalone version" even on LEDE 17.01.x for
creating backups (-b) as all used code is in sysupgrade itself.
However, I still use unchanged sysupgrade for flashing (passing the backup
archive using -f). Flashing depends on external files (/lib/upgrade)
whose changes might also depend on a sysupgrade change.

Regards,

---
      Luiz Angelo Daros de Luca
             luizluca at gmail.com