ripgrep: migrate to libripgrep

This commit does the work to delete the old `grep` crate and effectively
rewrite most of ripgrep core to use the new libripgrep crates. The new
`grep` crate is now a facade that collects the various crates that make
up libripgrep.

The most complex part of ripgrep core is now arguably the translation
between command line parameters and the library options, which is
ultimately where we want to be.

src/config.rs

@@ -12,10 +12,7 @@ use std::path::{Path, PathBuf};
 use Result;
 
 /// Return a sequence of arguments derived from ripgrep rc configuration files.
-///
-/// If no_messages is false and there was a problem reading a config file,
-/// then errors are printed to stderr.
-pub fn args(no_messages: bool) -> Vec<OsString> {
+pub fn args() -> Vec<OsString> {
     let config_path = match env::var_os("RIPGREP_CONFIG_PATH") {
         None => return vec![],
         Some(config_path) => {
@@ -28,20 +25,20 @@ pub fn args(no_messages: bool) -> Vec<OsString> {
     let (args, errs) = match parse(&config_path) {
         Ok((args, errs)) => (args, errs),
         Err(err) => {
-            if !no_messages {
-                eprintln!("{}", err);
-            }
+            message!("{}", err);
             return vec![];
         }
     };
-    if !no_messages && !errs.is_empty() {
+    if !errs.is_empty() {
         for err in errs {
-            eprintln!("{}:{}", config_path.display(), err);
+            message!("{}:{}", config_path.display(), err);
         }
     }
     debug!(
         "{}: arguments loaded from config file: {:?}",
-        config_path.display(), args);
+        config_path.display(),
+        args
+    );
     args
 }
 
@@ -59,7 +56,7 @@ fn parse<P: AsRef<Path>>(
     let path = path.as_ref();
     match File::open(&path) {
         Ok(file) => parse_reader(file),
-        Err(err) => errored!("{}: {}", path.display(), err),
+        Err(err) => Err(From::from(format!("{}: {}", path.display(), err))),
     }
 }