fix(host-rules): support matchHost with a dot prefix

[straub]

Changes:

host-rules will no longer double up on dot prefixes if the configured value of matchHost
already contains one.

Context:

I found myself wishing the docs called this out when I added my own dot prefix out of what
I thought was an abundance of caution, and inadvertently made it impossible to match any
hostnames due to the one already there :) Hoping to help clarify this for posterity.

Open to suggestions on the wording! I'm not sure I phrased this as clearly as possible or
kept the voice of the docs consistently.

Edit: updated per recommendation below to correct the behavior, in addition to clarifying
in the docs.

Documentation (please check one with an [x])

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• No documentation update is required

How I've tested my work (please tick one)

I have verified these changes via:

• Code inspection only, or
• Newly added/modified unit tests, or
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• Both unit tests + ran on a real repository

[rarkins]

Do you mean that we ended up with a "double dot" prefix when you first tried it?

[straub]

Exactly! I (incorrectly) configured ".docker.io" and matchesHost() wound up trying to do hostname.endsWith('..docker.io') here:

renovate/lib/util/host-rules.ts

Line 88 in b8e36da

return hostname === rule.matchHost || hostname.endsWith(`.${rule.matchHost}`);

[rarkins]

We could/should probably fix that though

[straub]

Sounds good to me! Something like rule.matchHost.startsWith('.') ? hostname.endsWith(rule.matchHost) : hostname.endsWith(.${rule.matchHost})?

Would we still want to have clarification in the docs that this happens?

Happy to PR this, with guidance on the desired approach. Also thanks for your time as always!

[rarkins]

I think that logic change sounds good. You're welcome to expand the explanation in the documentation too at the same time!

[straub]

@rarkins Updated! Please let me know what you think, at your convenience

[renovate-release]

🎉 This PR is included in version 26.18.0 🎉

The release is available on:

• GitHub release
• 26.18.0

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