Package via git: Allow ssh clone

[systemofapwne]

Right now, git upstream urls are limited to http(s), which is fine for publicly hosted git repos.
For private repos, one needs to supply credentials.

• Either via http url like http://user:password@domain.tld/the_repo.git or http://deploy-token@domain.tld/the_repo.git (Note: I did not test this functionality with AURCache but I expect this to work).
• Or via ssh keys: Valid git urls are then ssh://git@domain.tld/the_repo.git or just git@domain.tld:the_repo.git. One does need to supply an SSH key [1] however.

I propose, that the check at

AURCache/frontend/lib/components/new_package/wizard_git.dart

Line 59 in 927cd6f

if (!value.startsWith('http')) {

is either dropped or modified to support none http git upstream urls.

[1] This depends on rust's git2 library honoring ssh_config. One could then configure SSH keys and clone a repo via SSH.

[Lukas-Heiligenbrunner]

Hey, yes, thats a limitation for now.
I'll probably add list on a settings page where users cann add ssh-key + domain pairs to add credentials for git urls.
I didn't test your first option either, but it might work.