While looking at Arch's ABS, I noticed several mysterious 'upgpkg' files that seemed to be used for upgrading packages in an automated way. So, I began a search for a program that used these upgpkg files.

So, here is a brief history of the upgpkg program, as best as I can tell:

• 2008-08-31: Initial 0.1 version is posted to Arch BBS by abhidg https://bbs.archlinux.org/viewtopic.php?id=54453
• 2008-09-21: Is quickly included in to Daenyth's pkgtools package https://github.com/Daenyth/pkgtools / https://aur.archlinux.org/packages/pkgtools/ , where it will receive minor updates through 2014 (but no version bumps)
• 2008-12-19: It is included by Florian Pritz ("bluewind") in his bin scripts https://git.server-speed.net/users/flo/bin/ , where he develops it as a more sophisticated fork
• 2010-11-01: bluewind submits upgpkg 0.2 to arch-general for inclusion in devtools https://lists.archlinux.org/pipermail/arch-general/2010-November/016989.html
• 2010-11-02: bluewind submits upgpkg 0.3 to arch-general for inclusion in devtools https://lists.archlinux.org/pipermail/arch-general/2010-November/017018.html
• 2010-11-08: bluewind submits upgpkg 0.4 to arge-general for inclusion in devtools https://lists.archlinux.org/pipermail/arch-general/2010-November/017069.html
• 2011-11-07: bluewind pushes upgpkg 0.5 to git
• 2014-07-06: bluewind pushes upgpkg 0.6 to git
• 2015-12-05: bluewind makes most recent change to upgpkg

Confusingly, there is an outdated mirror/fork of Daenyth's pkgtools at https://git.archlinux.org/users/thomas/pkgtools.git/

So anyway, the real-est version of upgpkg is bluewind's at https://git.server-speed.net/users/flo/bin/tree/upgpkg . To give additional credibility to bluewind's version as the "real" version, each of the upgpkg files in Arch's ABS was committed by bluewind (these packages are packages/pacman-mirrorlist, packages/perl, and community/inxi).

I haven't evaluated the program itself very thoroughly; but it seems that it could be used to generalize the upgrading part of autobuilder.