refactor: use MFE refs caching for master branches

[gabor-boros]

This PR fixes https://github.com/overhangio/tutor-mfe/issues/161 by using the --keep-git-dir flag of the add command. The docker build step is cached if the branch is intact since the last build. However, if the branch is updated, the cache is invalidated and a new build is required -- as expected.

The image above shows that the first build had ditch the previous cache; the second build shows that the image is rebuilt with no changes on the branch, therefore it is cached.

cc: @regisb @arbrandes

[regisb]

It wouldn't. But we expect that people and companies that face rate limiting issues don't build from master branches, but tags.

[arbrandes]

companies that face rate limiting issues don't build from master branches, but tags

Ah, this makes sense. @gabor-boros, do you mind including in this PR a change to the README that gives people this particular tip?

[gabor-boros]

Reading back the comments, this raises a question for me: How would this solve the issue at all?

I mean, if the ADD command reaches out to GitHub to check if the cache need to be invalidated, we will hit the rate-limits again, but now only if the image is built for the master branches (many times). Right?

I guess we were not thinking about that @regisb. We were discussing to drop the caching like this during our call. Won't it make sense to do so?

[regisb]

I mean, if the ADD command reaches out to GitHub to check if the cache need to be invalidated, we will hit the rate-limits again, but now only if the image is built for the master branches (many times). Right?

Yes, this is correct. My reasoning is that this problem should not happen too often, if at all. And in particular, it should not affect your project. And when it does, you always have the option to create a plugin to remove the refs. Am I understanding this correctly?

[gabor-boros]

@regisb This is now ready for your review. Based on our latest discussion, it seems that would be the ultimate solution. I think every needs will be satisfied with this changes as:

• It is not calling out to API, hence no authentication is needed because of the rate limits
• The caching still works as intended
• The code is simplified
• We added a feature with this change (as a side effect): private repositories could be cloned and cached as well

[gabor-boros]

@regisb Sure thing. I'll do it by EOD

[arbrandes]

I think this would be good to get in Quince. Mind making those changes, @gabor-boros?

[regisb]

@gabor-boros if you don't have time that's fine too, I can make the change today. We're in a bit of a rush with the upcoming Quince release...

[gabor-boros]

Hey @regisb, sorry, I ran out of time. If you can help out that would be awesome!

[regisb]

Superseded by https://github.com/overhangio/tutor-mfe/commit/c4ed70cf4e25a1c16b6945e2b73af47d82d31000 Thanks a lot for your help @gabor-boros!