explain the options bootstrap passes to curl

src/bootstrap/bootstrap.py

@@ -106,22 +106,29 @@ def _download(path, url, probably_big, verbose, exception):
 
     try:
         if (probably_big or verbose) and "GITHUB_ACTIONS" not in os.environ:
-            option = "-#"
+            option = "--progress-bar"
         else:
-            option = "-s"
+            option = "--silent"
         # If curl is not present on Win32, we should not sys.exit
         #   but raise `CalledProcessError` or `OSError` instead
         require(["curl", "--version"], exception=platform_is_win32())
         extra_flags = []
         if curl_version() > (7, 70):
             extra_flags = [ "--retry-all-errors" ]
+        # options should be kept in sync with
+        # src/bootstrap/src/core/download.rs
+        # for consistency.
+        # they are also more compreprensivly explained in that file.
         run(["curl", option] + extra_flags + [
-            "-L", # Follow redirect.
-            "-y", "30", "-Y", "10",    # timeout if speed is < 10 bytes/sec for > 30 seconds
-            "--connect-timeout", "30",  # timeout if cannot connect within 30 seconds
-            "-o", path,
+            # Follow redirect.
+            "--location",
+            # timeout if speed is < 10 bytes/sec for > 30 seconds
+            "--speed-time", "30", "--speed-limit", "10",
+            # timeout if cannot connect within 30 seconds
+            "--connect-timeout", "30",
+            "--output", path,
             "--continue-at", "-",
-            "--retry", "3", "-SRf", url],
+            "--retry", "3", "--show-error", "--remote-time", "--fail", url],
             verbose=verbose,
             exception=True, # Will raise RuntimeError on failure
         )

src/bootstrap/src/core/download.rs

@@ -227,25 +227,42 @@ impl Config {
     fn download_http_with_retries(&self, tempfile: &Path, url: &str, help_on_error: &str) {
         println!("downloading {url}");
         // Try curl. If that fails and we are on windows, fallback to PowerShell.
+        // options should be kept in sync with
+        // src/bootstrap/src/core/download.rs
+        // for consistency
         let mut curl = command("curl");
         curl.args([
-            "-y",
+            // follow redirect
+            "--location",
+            // timeout if speed is < 10 bytes/sec for > 30 seconds
+            "--speed-time",
             "30",
-            "-Y",
-            "10", // timeout if speed is < 10 bytes/sec for > 30 seconds
+            "--speed-limit",
+            "10",
+            // timeout if cannot connect within 30 seconds
             "--connect-timeout",
-            "30", // timeout if cannot connect within 30 seconds
-            "-o",
+            "30",
+            // output file
+            "--output",
             tempfile.to_str().unwrap(),
+            // if there is an error, don't restart the download,
+            // instead continue where it left off.
             "--continue-at",
             "-",
+            // retry up to 3 times.  note that this means a maximum of 4
+            // attempts will be made, since the first attempt isn't a *re*try.
             "--retry",
             "3",
-            "-SRf",
+            // show errors, even if --silent is specified
+            "--show-error",
+            // set timestamp of downloaded file to that of the server
+            "--remote-time",
+            // fail on non-ok http status
+            "--fail",
         ]);
         // Don't print progress in CI; the \r wrapping looks bad and downloads don't take long enough for progress to be useful.
         if CiEnv::is_ci() {
-            curl.arg("-s");
+            curl.arg("--silent");
         } else {
             curl.arg("--progress-bar");
         }