fix: Resolve '400 Custom domains' error on GitHub Enterprise Server

[atilsensalduz]

This PR fixes an issue with the UpdatePages method, which caused the error: "400 Custom domains are not available for GitHub Pages" on GHES. The issue occurred because the update struct didn't specify the omitempty tag for JSON marshalling, which resulted in explicit null values being sent. As a result, GHES returned the error.

To resolve this, the fix adds a check for the client URL. If the URL differs from the public GitHub API, a new struct is created without the CNAME field to avoid sending null values.

Question: Should we add the omitempty tag directly to the CNAME field of the PagesUpdate struct instead of this workaround?

References:

• Issue: UpdatePages method doesn't work on github enterprise server (CNAME argument not allowed) #3466

Fixes: #3466.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 91.03%. Comparing base (868f897) to head (f7cf4e6).
Report is 4 commits behind head on master.

Additional details and impacted files

@@           Coverage Diff           @@
##           master    #3489   +/-   ##
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  Coverage   91.02%   91.03%           
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  Files         179      179           
  Lines       15561    15574   +13     
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+ Hits        14165    14178   +13     
  Misses       1223     1223           
  Partials      173      173           

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[gmlewis]

What happens when a person wishes to remove a custom domain?

When this happens for other endpoints (where sending a "null" is important and has a specific meaning), we often introduce a second endpoint that has serves the other usage, and whose name highlights the difference between the two use cases.

I think that might be appropriate here.

If you look around, you should be able to find some endpoints like that, but if you can't, let me know and I'll dig around for examples of this.

[atilsensalduz]

What happens when a person wishes to remove a custom domain?

When this happens for other endpoints (where sending a "null" is important and has a specific meaning), we often introduce a second endpoint that has serves the other usage, and whose name highlights the difference between the two use cases.

I think that might be appropriate here.

If you look around, you should be able to find some endpoints like that, but if you can't, let me know and I'll dig around for examples of this.

You're absolutely right. Thanks for guiding me toward the better approach. I've updated the PR to use a separate endpoint for updating pages specifically for GHES and to use a struct without the CNAME field to avoid the 400 error.

[gmlewis]

Thank you, @atilsensalduz!
LGTM.

Awaiting second LGTM+Approval from any other contributor to this repo before merging.

@stevehipwell - might you have time for a coffee review? Thank you!

[gmlewis]

Whups, I spoke too soon. Please fix the lint issues by following step 4 of CONTRIBUTING.md.

[atilsensalduz]

Whups, I spoke too soon. Please fix the lint issues by following step 4 of CONTRIBUTING.md.

Ah, sorry about that! I must have missed it. 🤦 Thanks for the heads-up! I've fixed the lint issues now. I really appreciate your review and support! @gmlewis

[stevehipwell]

LGTM

[gmlewis]

Thank you, @stevehipwell!
Merging.