posix/sh: add basic logging to the parser

We use `env_logger` to display the messages, which ends up pulling
in some heavy crates (e.g. `regex`), so the binary size has
increased.  We may want to look at other loggers.

Author: Arcterus

Cargo.lock

@@ -39,7 +39,7 @@ chmod = ["libmesabox/chmod"]
 echo = ["libmesabox/echo"]
 false = ["libmesabox/false"]
 head = ["libmesabox/head"]
-sh = ["libmesabox/sh"]
+sh = ["libmesabox/sh", "env_logger"]
 sleep = ["libmesabox/sleep"]
 true = ["libmesabox/true"]
 uname = ["libmesabox/uname"]
@@ -97,7 +97,8 @@ default = ["unix"]
 [workspace]
 
 [dependencies]
-libmesabox = { path = "libmesabox" }
+libmesabox = { path = "libmesabox", default-features = false }
+env_logger = { version = "0.5.11", optional = true }
 
 [dev-dependencies]
 tempfile = "3.0.2"

Cargo.toml

@@ -37,7 +37,7 @@ chmod = ["walkdir", "uucore"]
 echo = []
 false = []
 head = []
-sh = ["nom", "glob", "rustyline", "libc"]
+sh = ["nom", "glob", "rustyline", "libc", "log"]
 sleep = ["uucore"]
 true = []
 uname = ["platform-info"]
@@ -118,3 +118,4 @@ fnv = { version = "1.0.6", optional = true }
 nom = { version = "4.0.0", features = ["verbose-errors"], optional = true }
 #rustyline = { version = "1.0.0", optional = true }
 rustyline = { git = "https://github.com/kkawakam/rustyline", optional = true }
+log = { version = "0.4.3", optional = true }

libmesabox/Cargo.toml

@@ -52,6 +52,9 @@ extern crate glob;
 extern crate platform_info;
 #[cfg(feature = "rustyline")]
 extern crate rustyline;
+#[cfg(feature = "log")]
+#[macro_use]
+extern crate log;
 
 use clap::{App, SubCommand};
 use std::env::{self, VarsOs};