Improve repository selection, based on prefixes in config and full image name

[vsychov]

Hello everyone,

This code solves a problem that occurs with DigitalOcean repositories when you have multiple repositories in different projects with different credentials.

For example:

registries:
  - api_url: https://registry.digitalocean.com
    credentials: pullsecret:infra/registry-project1
    name: Project 1
    ping: false
    prefix: registry.digitalocean.com/project1
  - api_url: https://registry.digitalocean.com
    credentials: pullsecret:infra/registry-project2
    name: Project 2
    ping: false
    prefix: registry.digitalocean.com/project2

Previously, image-updater ignored this configuration and only used "https://registry.digitalocean.com" because it could not find an exact repository match.
This PR fixes this problem so that the above configuration will work.

[codecov-commenter]

Codecov Report

Merging #547 (7d33223) into master (49825ec) will increase coverage by 0.20%.
The diff coverage is 100.00%.

@@            Coverage Diff             @@
##           master     #547      +/-   ##
==========================================
+ Coverage   65.76%   65.96%   +0.20%     
==========================================
  Files          21       21              
  Lines        2039     2051      +12     
==========================================
+ Hits         1341     1353      +12     
  Misses        569      569              
  Partials      129      129              

Impacted Files	Coverage Δ
pkg/argocd/update.go	69.79% <100.00%> (ø)
pkg/registry/endpoints.go	75.53% <100.00%> (+2.31%)	⬆️

📣 We’re building smart automated test selection to slash your CI/CD build times. Learn more

[vsychov]

Also in this PR I fixed pipeline (linter didn't works), @jannfis can you review pls?

[jannfis]

Thanks @vsychov - this change is reasonable to me, and I'd like it to go in! I'll try to carve out some time for review really soon.

[vsychov]

Hello @jannfis, is it ok to be merged?

[vsychov]

Hello @jannfis , any updates on that?

[vsychov]

Hi guys, can it be merged?