if JULIAUP_SERVER matches default, skip the check

Author: johnnychen94

src/utils.rs

@@ -14,9 +14,28 @@ static NIGHTLY_SERVER_SUPPORTS_ETAG: OnceLock<bool> = OnceLock::new();
 /// to track versions of these builds.
 ///
 /// The result is cached after the first check.
+/// If JULIAUP_SERVER equals the default official ones, it works as usual (assumes ETAG support).
+/// Otherwise, sends a HEAD check request to verify ETAG support.
 #[cfg(not(windows))]
 pub fn check_server_supports_nightlies() -> Result<bool> {
     Ok(*NIGHTLY_SERVER_SUPPORTS_ETAG.get_or_init(|| {
+        // Check if JULIAUP_SERVER equals the default official one
+        let is_default_server = {
+            let julia_server = std::env::var("JULIAUP_SERVER")
+                .unwrap_or_else(|_| "https://julialang-s3.julialang.org".to_string());
+            
+            // Normalize URL (remove trailing slashes for comparison)
+            let julia_server_normalized = julia_server.trim_end_matches('/');
+            
+            julia_server_normalized == "https://julialang-s3.julialang.org"
+        };
+
+        // If using default official servers, assume ETAG support
+        if is_default_server {
+            return true;
+        }
+
+        // For custom servers, check via HEAD request
         let base_url = match get_julianightlies_base_url() {
             Ok(url) => url,
             Err(_) => return false,
@@ -40,6 +59,8 @@ pub fn check_server_supports_nightlies() -> Result<bool> {
 /// to track versions of these builds.
 ///
 /// The result is cached after the first check.
+/// If JULIAUP_SERVER equals the default official ones, it works as usual (assumes ETAG support).
+/// Otherwise, sends a HEAD check request to verify ETAG support.
 #[cfg(windows)]
 pub fn check_server_supports_nightlies() -> Result<bool> {
     use windows::core::HSTRING;
@@ -49,6 +70,23 @@ pub fn check_server_supports_nightlies() -> Result<bool> {
     use windows::Web::Http::HttpRequestMessage;
 
     Ok(*NIGHTLY_SERVER_SUPPORTS_ETAG.get_or_init(|| {
+        // Check if JULIAUP_SERVER equals the default official one
+        let is_default_server = {
+            let julia_server = std::env::var("JULIAUP_SERVER")
+                .unwrap_or_else(|_| "https://julialang-s3.julialang.org".to_string());
+            
+            // Normalize URL (remove trailing slashes for comparison)
+            let julia_server_normalized = julia_server.trim_end_matches('/');
+            
+            julia_server_normalized == "https://julialang-s3.julialang.org"
+        };
+
+        // If using default official servers, assume ETAG support
+        if is_default_server {
+            return true;
+        }
+
+        // For custom servers, check via HEAD request
         let base_url = match get_julianightlies_base_url() {
             Ok(url) => url,
             Err(_) => return false,