pkg updates always except when needed

[jmgurney]

I've noticed that pkg almost always updates itself. Even when I recently ran pkg just a few minutes before. Just now, the pkg versions were rolled to 1200076, and it didn't update the database resulting in checksum mismatches, until I ran pkg update -f. I believe that the logic for detecting when an update is needed is not functioning correctly. I'm pretty sure that the last update was 1200075 because of the error message that I get later, so I know when an update actually happens.

Example of it failing:

# pkg search arcanist
arcanist-php56-20180420_1      Command line interface for Phabricator
arcanist-php70-20180420_1      Command line interface for Phabricator
arcanist-php71-20180420_1      Command line interface for Phabricator
arcanist-php72-20180420_1      Command line interface for Phabricator
root@generic:/usr/src/sys # pkg install arcanist-php72
Updating FreeBSD repository catalogue...
FreeBSD repository is up to date.
All repositories are up to date.
The following 16 package(s) will be affected (of 0 checked):

New packages to be INSTALLED:
	arcanist-php72: 20180420_1
	php72-simplexml: 7.2.8
	libxml2: 2.9.7
	php72: 7.2.8
	libargon2: 20171227
	pcre: 8.42
	php72-dom: 7.2.8
	php72-hash: 7.2.8
	php72-curl: 7.2.8
	curl: 7.60.0
	libnghttp2: 1.32.0
	php72-json: 7.2.8
	php72-libphutil: 20180420
	php72-xml: 7.2.8
	php72-mbstring: 7.2.8
	oniguruma: 6.8.2

Number of packages to be installed: 16

The process will require 56 MiB more space.
9 MiB to be downloaded.

Proceed with this action? [y/N]: y
[1/16] Fetching arcanist-php72-20180420_1.txz:  44%  240 KiB 245.8kB/s    00:01 [1/16] Fetching arcanist-php72-20180420_1.txz: 100%  539 KiB 552.4kB/s    00:01    
pkg: cached package arcanist-php72-20180420_1: size mismatch, fetching from remote
[2/16] Fetching arcanist-php72-20180420_1.txz: 100%  539 KiB 552.4kB/s    00:01    
pkg: cached package arcanist-php72-20180420_1: size mismatch, cannot continue

If you notice it thinks the FreeBSD repo is up to date. This happened for all the arcanist php versions.

Bare pkg update also thinks it's ok:

# pkg update
Updating FreeBSD repository catalogue...
FreeBSD repository is up to date.
All repositories are up to date.

Then I manually run pkg update -f:

# pkg update -f
Updating FreeBSD repository catalogue...
Fetching meta.txz: 100%    944 B   0.9kB/s    00:01    
Fetching packagesite.txz: 100%    5 MiB   1.8MB/s    00:03    
Processing entries:   0%
Newer FreeBSD version for package php70-pear-Date_Holidays_Norway:
To ignore this error set IGNORE_OSVERSION=yes
- package: 1200076
- running kernel: 1200072
Allow missmatch now?[Y/n]: y   
Processing entries: 100%
FreeBSD repository update completed. 26582 packages processed.
All repositories are up to date.

And then after that, arcanist installs fine. (Yes, I know about the missmatch, it's not causing a problem for the ports I'm installing.)

This is on a July 9th arm64 snapshot w/ a recent kernel:
FreeBSD generic 12.0-CURRENT FreeBSD 12.0-CURRENT #3 r337535M: Fri Aug 10 03:23:24 UTC 2018 freebsd@generic:/usr/src/sys/arm64/compile/GENERIC arm64

[brd]

There is a race condition when the pkg sets are deployed.

Duplicate of #988.