Update warning text

src/cli.rs

@@ -186,7 +186,7 @@ fn build_command() -> Command<'static> {
                 .help("Set the shell to use for executing benchmarked commands. This can be the \
                        name or the path to the shell executable, or a full command line \
                        like \"bash --norc\". It can also be set to \"default\" to explicitly select \
-                       the default shell on this patform. Finally, this can also be set to \
+                       the default shell on this platform. Finally, this can also be set to \
                        \"none\" to disable the shell. In this case, commands will be executed \
                        directly. They can still have arguments, but more complex things like \
                        \"sleep 0.1; sleep 0.2\" are not possible without a shell.")

src/output/warnings.rs

@@ -17,7 +17,10 @@ impl fmt::Display for Warnings {
         match *self {
             Warnings::FastExecutionTime => write!(
                 f,
-                "Command took less than {:.0} ms to complete. Results might be inaccurate.",
+                "Command took less than {:.0} ms to complete. Note that the results might be \
+                inaccurate because hyperfine can not calibrate the shell startup time much \
+                more precise than this limit. You can try to use the `-N`/`--shell=none` \
+                option to disable the shell completely.",
                 MIN_EXECUTION_TIME * 1e3
             ),
             Warnings::NonZeroExitCode => write!(f, "Ignoring non-zero exit code."),