From b34a41797248fb36dd690d6013a9a238391437d0 Mon Sep 17 00:00:00 2001
From: "Felix S. Klock II" <pnkfelix@pnkfx.org>
Date: Mon, 15 Jun 2020 15:02:57 -0400
Subject: [PATCH] Add more info to `x.py build --help` on default value for `-j
 JOBS`.

---
 src/bootstrap/flags.rs | 7 ++++++-
 1 file changed, 6 insertions(+), 1 deletion(-)

diff --git a/src/bootstrap/flags.rs b/src/bootstrap/flags.rs
index cfaa43f397095..3726115357436 100644
--- a/src/bootstrap/flags.rs
+++ b/src/bootstrap/flags.rs
@@ -149,7 +149,12 @@ To learn more about a subcommand, run `./x.py <subcommand> -h`",
             "N",
         );
         opts.optopt("", "src", "path to the root of the rust checkout", "DIR");
-        opts.optopt("j", "jobs", "number of jobs to run in parallel", "JOBS");
+        let j_msg = format!(
+            "number of jobs to run in parallel; \
+             defaults to {} (this host's logical CPU count)",
+            num_cpus::get()
+        );
+        opts.optopt("j", "jobs", &j_msg, "JOBS");
         opts.optflag("h", "help", "print this help message");
         opts.optopt(
             "",