Use a fallback mirror for code.dlang.org

[wilzbach]

As #218 doesn't seem to be moving forward, I have uploaded all DUB releases to GitHub, which should be much more reliable (see dlang/dub#1290 for details).
At the moment, there isn't a mirror for code.dlang.org/download/LATEST (we should probably create a gh-pages repo like LDC or use an S3 bucket), so for now I simply used the GitHub API. I know that it's rate-limited, but imho having a chance to succeed is a lot better than having none.

If code.dlang.org is down, we still manage to get the latest DUB:

dmd-2.077.1 already installed
curl: (7) Failed to connect to code.dlang.org port 80: Connection refused
curl: (7) Failed to connect to code.dlang.org port 80: Connection refused
curl: (7) Failed to connect to code.dlang.org port 80: Connection refused
curl: (7) Failed to connect to code.dlang.org port 80: Connection refused
curl: (7) Failed to connect to code.dlang.org port 80: Connection refused
Failed to download 'http://code.dlang.org/download/LATEST'
Downloading and unpacking http://code.dlang.org/files/dub-1.6.0-linux-x86_64.tar.gz

curl: (7) Failed to connect to code.dlang.org port 80: Connection refused
Downloading and unpacking https://github.com/dlang/dub/releases/download/v1.6.0/dub-1.6.0-linux-x86_64.tar.gz
######################################################################## 100.0%

Run `source ~/dlang/dmd-2.077.1/activate` in your shell to use dmd-2.077.1.
This will setup PATH, LIBRARY_PATH, LD_LIBRARY_PATH, DMD, DC, and PS1.
Run `deactivate` later on to restore your environment.

[dlang-bot]

Thanks for your pull request, @wilzbach!

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[wilzbach]

This will be replaced soon once an actual mirror for LATEST exists

[wilzbach]

Are you okay with adding this fallback mirror @MartinNowak?

[wilzbach]

What's wrong with this? Code.dlang.org is often down and we mirrored all dub releases to GitHub.
Also only DMD and LDC ship with dub

[wilzbach]

A few things have changed here:

1. People are still using GDC and old DMD compilers and experience failures due to code.dlang.org being down
2. There's https://dlang.github.io/dub/LATEST now (see Can we switch to hosting the DUB binaries on GitHub? dub#1290 (comment)), so now workarounds will be needed
3. There's Use fallback mirrors in the install script #291 which adds mirroring capability to fetch and download

-> I'm reopening this, s.t. it doesn't get forgotten and I will revive and rebase it once #291 has been merged.

[wilzbach]

I will revive and rebase it once #291 has been merged.

Done. Also note that the DUB binaries will soon be auto-deployed to GitHub, s.t. code.dlang.org/download might be retired.

[wilzbach]

Going to merge this now as the errors are still a thing, I'm tired of waiting for such a simple fix and the backup "mirror" now got the primary "upstream" for the binaries.

[MartinNowak]

Why not https?

[wilzbach]

I think simply because it wasn't using https before

[MartinNowak]

Sorry, must have forgotten to submit a comment or accidentally hit the close button. Definitely helpful in the short-term.

It's still a bit unfortunate that dub releases are lingering between dlang.org and code.dlang.org (and now GH).
I'm not particularly convinced that we want to go further into GH releases as they are quite cumbersome and rely on quite a lot of services.

How about just archiving old dub releases that preceed the dmd integration.
I'm also open to extract separate binary dub tars/zips from the official releases and publish them on the existing release pipeline.

My main point here is to avoid the maintenance overhead of a second release pipeline when we already have established infrastructure and processes in place.