Use api subdomain for REST and GQL clients when host is tenant

pkg/api/graphql_client_test.go

@@ -293,6 +293,11 @@ func TestGraphQLEndpoint(t *testing.T) {
 			host:         "enterprise.com",
 			wantEndpoint: "https://enterprise.com/api/graphql",
 		},
+		{
+			name:         "tenant",
+			host:         "tenant.ghe.com",
+			wantEndpoint: "https://api.tenant.ghe.com/graphql",
+		},
 	}
 
 	for _, tt := range tests {

pkg/api/http_client.go

@@ -135,7 +135,14 @@ func isGarage(host string) bool {
 }
 
 func isEnterprise(host string) bool {
-	return host != github && host != localhost
+	return host != github && host != localhost && !isTenancy(host)
+}
+
+// tenancyHost is the domain name of a tenancy GitHub instance.
+const tenancyHost = "ghe.com"
+
+func isTenancy(host string) bool {
+	return strings.HasSuffix(host, "."+tenancyHost)
 }
 
 func normalizeHostname(hostname string) string {
@@ -146,6 +153,14 @@ func normalizeHostname(hostname string) string {
 	if strings.HasSuffix(hostname, "."+localhost) {
 		return localhost
 	}
+	// This has been copied over from the cli/cli NormalizeHostname function
+	// to ensure compatible behaviour but we don't fully understand when or
+	// why it would be useful here. We can't see what harm will come of
+	// duplicating the logic.
+	if before, found := strings.CutSuffix(hostname, "."+tenancyHost); found {
+		idx := strings.LastIndex(before, ".")
+		return fmt.Sprintf("%s.%s", before[idx+1:], tenancyHost)
+	}
 	return hostname
 }
 

pkg/api/rest_client_test.go

@@ -474,6 +474,11 @@ func TestRestPrefix(t *testing.T) {
 			host:         "enterprise.com",
 			wantEndpoint: "https://enterprise.com/api/v3/",
 		},
+		{
+			name:         "tenant",
+			host:         "tenant.ghe.com",
+			wantEndpoint: "https://api.tenant.ghe.com/",
+		},
 	}
 
 	for _, tt := range tests {