Allow installation (with updates) of PKGBUILDs in "third party" Git repos.

[origintopleft]

Some friends of mine were talking about a Minecraft server, so I installed multimc-bin from the AUR and discovered the PKGBUILD maintained there is out of date. MultiMC has a built-in updater function, but for some reason this is hardcoded to write in /usr/lib/update, which naturally doesn't work. Upstream's proposed solution is to use their own PKGBUILD.

The problem is, this requires manual maintenance. There seems to be no way to convince pikaur (or indeed any AUR helper) to check for updates from PKGBUILDs outside of the AUR as part of pikaur -Syu or similar. This effectively invalidates much of why I was using an AUR helper in the first place, since if I have to manually invoke makepkg and pull the Git repository, I might as well go lower level and ./configure --prefix=$HOME/opt/multimc instead.

What I'm requesting is some way to invoke something like this:

pikaur -P https://github.com/MultiMC/multimc-pkgbuild.git

and have future updates be managed as part of a standard pikaur -Syu invocation (perhaps requiring --devel --needed consistent with *-git packages on the AUR).

[actionless]

yeah, this could be potentially useful for wider community, because some people have collections of PKGBUILDs which for this or others reasons can't be pushed to AUR

but there is some caveat to it, and also to pikaur -P https://github.com/MultiMC/multimc-pkgbuild.git proposed example:

the file structure could either:

1. following aur principles - one repo = one aur package
2. one-level directory structure, inside each dir PKGBUILD
3. some other arbitrary more complicated structures

and from my practical experience all 3 options could be seen on github same often, but only 1 and 2 sounds like smth reasonable to take a try to develop

so as a quick summary, potential action points you could take to implement the things you want:

0. implement helper func which extract pkgbuilds from git repo following 1/2 logic
   0.1) that would also require introducing new config option for location path for storing git repos after initial cloning and pull-ing them next. also lots of git logic already implemented in PackageBuild class, so would be nice to find a way to keep it not duplicating the same code, but mb extracting working with git repos into separate class and reusing that class
1. adding support for 0 in -P
2. adding support for 0 in -U
   2.1) which obviously require also adding a config option for adding such repos, and mb specifying which filestructrure each of the repos is using

feel free to ask more questions

[actionless]

also this seems to be quite similar technically as well: #895 , so i guess it could be implemented similar-ish, just as a third repo type