fix(libfetchers): set GitHub API version header, closes #255

Sets the `X-GitHub-Api-Version` header to `2022-11-28` for calls to the
GitHub API.
This follows the later version as per
https://docs.github.com/en/rest/about-the-rest-api/api-versions?apiVersion=2022-11-28.

This affected the check on whether to use the API versus unauthenticated
calls as well, given the headers would no longer be empty if the
authentication token were missing.
The workaround used here is to use a check similar to an existing
check for the token.

In the current implementation, headers are (still) similarly sent to
non-authenticated as well as GitHub on-prem calls.
For what it's worth, manual curl calls with such a header seemed to
break nor unauthenticated calls nor ones to the github.com API.

Change-Id: I6e10839e6b99cb65eb451e923b2a64f5d3c0f578

doc/manual/change-authors.yml

@@ -78,6 +78,9 @@ jade:
   forgejo: jade
   github: lf-
 
+kiara:
+  github: KiaraGrouwstra
+
 kjeremy:
   github: kjeremy
 

doc/manual/rl-next/x-github-api-header.md

@@ -0,0 +1,23 @@
+---
+synopsis: "Set `X-GitHub-Api-Version` header"
+issues: [fj#255]
+cls: [1925]
+category: Development
+credits: kiara
+---
+
+Sets the `X-GitHub-Api-Version` header to `2022-11-28` for calls to the
+GitHub API.
+This follows the later version as per
+https://docs.github.com/en/rest/about-the-rest-api/api-versions?apiVersion=2022-11-28.
+
+This affected the check on whether to use the API versus unauthenticated
+calls as well, given the headers would no longer be empty if the
+authentication token were missing.
+The workaround to this used here is to use a check similar to an existing
+check for the token.
+
+In the current implementation, headers are (still) similarly sent to
+non-authenticated as well as GitHub on-prem calls.
+For what it's worth, manual curl calls with such a header seemed to
+break nor unauthenticated calls nor ones to the github.com API.

src/libfetchers/github.cc

@@ -290,7 +290,7 @@ struct GitHubInputScheme : GitArchiveInputScheme
         const auto urlFmt =
             host != "github.com"
                 ? "https://%s/api/v3/repos/%s/%s/tarball/%s"
-            : headers.empty()
+                : !getAccessToken(host)
                     ? "https://%s/%s/%s/archive/%s.tar.gz"
                     : "https://api.%s/repos/%s/%s/tarball/%s";
 
@@ -308,6 +308,13 @@ struct GitHubInputScheme : GitArchiveInputScheme
             .applyOverrides(input.getRef(), input.getRev())
             .clone(destDir);
     }
+
+    Headers makeHeadersWithAuthTokens(const std::string & host) const
+    {
+        Headers headers = GitArchiveInputScheme::makeHeadersWithAuthTokens(host);
+        headers.emplace_back("X-GitHub-Api-Version", "2022-11-28");
+        return headers;
+    }
 };
 
 struct GitLabInputScheme : GitArchiveInputScheme