Fix GitHub Actions Cache setting an incorrect Content-Range header

[j-mie]

I recently tried to use the VCPKG_BINARY_SOURCES setting to set clear;x-gha,readwrite in our GitHub Actions workflow and couldn't get vcpkg to upload to the cache successfully. Proxying vcpkg I noticed that the Content-Range header was off by one causing the cache server to return:

HTTP/2 400 Bad Request
Content-Length: 295
Content-Type: application/json; charset=utf-8
Date: Wed, 15 Jan 2025 02:35:10 GMT
Server: Kestrel
Cache-Control: no-store,no-cache
Pragma: no-cache
...
X-Frame-Options: SAMEORIGIN

{"$id":"1","innerException":null,"message":"The size of the content did not match the Content-Range header","typeName":"Microsoft.Azure.DevOps.ArtifactCache.WebApi.InvalidChunkException, Microsoft.Azure.DevOps.ArtifactCache.WebApi","typeKey":"InvalidChunkException","errorCode":0,"eventId":3000}

Manually correcting the value and then sealing the cache with the POST request containing the size field resulted in the package being correctly cached. I'm not sure why users of the GitHub Actions binary caching feature in vcpkg haven't run into this on github.com and haven't had the time to see if github.com handles this case differently but it does work on GitHub Enterprise Server.

[BillyONeal]

Needs to be guarded for cache_size == 0. Probably by another if around the if on line 927, or an early return.

Also it seems like it would be a good idea to fill in the size based on https://developer.mozilla.org/docs/Web/HTTP/Headers/Content-Range ?

Suggested change

	"Content-Range: bytes 0-" + std::to_string(cache_size - 1) + "/*",
	fmt::format("Content-Range: bytes 0-{}/{}", cache_size - 1, cache_size),

[j-mie]

I'll fix that now

Regarding the size, the enterprise backend doesn't seem to mind if you set it or not, I think it's probably more relevant when using chunking as in #1043 but will also fix.

[BillyONeal]

Thanks for the fix!