auto merge of #9096 : huonw/rust/linenoise, r=brson

- Wrap calls into linenoise in a mutex so that the functions don't have to be `unsafe` any more (fixes #3921)
- Stop leaking every line that linenoise reads.
- Handle the situation of `rl::complete(some_function); do spawn { rl::read(""); }` which would crash (`fail!` that turned into an abort, possibly due to failing with the lock locked) when the user attempted to tab-complete anything.
- Add a test for the various functions; it has to be run by hand to verify anything works, but it won't bitrot.

src/test/run-pass/rl-human-test.rs

@@ -0,0 +1,75 @@
+// Copyright 2013 The Rust Project Developers. See the COPYRIGHT
+// file at the top-level directory of this distribution and at
+// http://rust-lang.org/COPYRIGHT.
+//
+// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
+// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
+// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
+// option. This file may not be copied, modified, or distributed
+// except according to those terms.
+
+// xfail-fast no compile flags for check-fast
+
+// we want this to be compiled to avoid bitrot, but the actual test
+//has to be conducted by a human, i.e. someone (you?) compiling this
+//file with a plain rustc invocation and running it and checking it
+//works.
+
+// compile-flags: --cfg robot_mode
+
+extern mod extra;
+use extra::rl;
+
+static HISTORY_FILE: &'static str = "rl-human-test-history.txt";
+
+fn main() {
+    // don't run this in robot mode, but still typecheck it.
+    if !cfg!(robot_mode) {
+        println("~~ Welcome to the rl test \"suite\". ~~");
+        println!("Operations:
+ - restrict the history to 2 lines,
+ - set the tab-completion to suggest three copies of each of the last 3 letters (or 'empty'),
+ - add 'one' and 'two' to the history,
+ - save it to `{0}`,
+ - add 'three',
+ - prompt & save input (check the history & completion work and contains only 'two', 'three'),
+ - load from `{0}`
+ - prompt & save input (history should be 'one', 'two' again),
+ - prompt once more.
+
+The bool return values of each step are printed.",
+                 HISTORY_FILE);
+
+        println!("restricting history length: {}", rl::set_history_max_len(3));
+
+        do rl::complete |line, suggest| {
+            if line.is_empty() {
+                suggest(~"empty")
+            } else {
+                for c in line.rev_iter().take(3) {
+                    suggest(format!("{0}{1}{1}{1}", line, c))
+                }
+            }
+        }
+
+        println!("adding 'one': {}", rl::add_history("one"));
+        println!("adding 'two': {}", rl::add_history("two"));
+
+        println!("saving history: {}", rl::save_history(HISTORY_FILE));
+
+        println!("adding 'three': {}", rl::add_history("three"));
+
+        match rl::read("> ") {
+            Some(s) => println!("saving input: {}", rl::add_history(s)),
+            None => return
+        }
+        println!("loading history: {}", rl::load_history(HISTORY_FILE));
+
+        match rl::read("> ") {
+            Some(s) => println!("saving input: {}", rl::add_history(s)),
+            None => return
+        }
+
+        rl::read("> ");
+    }
+}