grep-cli: introduce new grep-cli crate

This commit moves a lot of "utility" code from ripgrep core into
grep-cli. Any one of these things might not be worth creating a new
crate, but combining everything together results in a fair number of a
convenience routines that make up a decent sized crate.

There is potentially more we could move into the crate, but much of what
remains in ripgrep core is almost entirely dealing with the number of
flags we support.

In the course of doing moving things to the grep-cli crate, we clean up
a lot of gunk and improve failure modes in a number of cases. In
particular, we've fixed a bug where other processes could deadlock if
they write too much to stderr.

Fixes #990

grep-printer/src/color.rs

@@ -4,6 +4,25 @@ use std::str::FromStr;
 
 use termcolor::{Color, ColorSpec, ParseColorError};
 
+/// Returns a default set of color specifications.
+///
+/// This may change over time, but the color choices are meant to be fairly
+/// conservative that work across terminal themes.
+///
+/// Additional color specifications can be added to the list returned. More
+/// recently added specifications override previously added specifications.
+pub fn default_color_specs() -> Vec<UserColorSpec> {
+    vec![
+        #[cfg(unix)]
+        "path:fg:magenta".parse().unwrap(),
+        #[cfg(windows)]
+        "path:fg:cyan".parse().unwrap(),
+        "line:fg:green".parse().unwrap(),
+        "match:fg:red".parse().unwrap(),
+        "match:style:bold".parse().unwrap(),
+    ]
+}
+
 /// An error that can occur when parsing color specifications.
 #[derive(Clone, Debug, Eq, PartialEq)]
 pub enum ColorError {
@@ -227,6 +246,15 @@ impl ColorSpecs {
         merged
     }
 
+    /// Create a default set of specifications that have color.
+    ///
+    /// This is distinct from `ColorSpecs`'s `Default` implementation in that
+    /// this provides a set of default color choices, where as the `Default`
+    /// implementation provides no color choices.
+    pub fn default_with_color() -> ColorSpecs {
+        ColorSpecs::new(&default_color_specs())
+    }
+
     /// Return the color specification for coloring file paths.
     pub fn path(&self) -> &ColorSpec {
         &self.path

grep-printer/src/lib.rs

@@ -83,7 +83,7 @@ extern crate serde_derive;
 extern crate serde_json;
 extern crate termcolor;
 
-pub use color::{ColorError, ColorSpecs, UserColorSpec};
+pub use color::{ColorError, ColorSpecs, UserColorSpec, default_color_specs};
 #[cfg(feature = "serde1")]
 pub use json::{JSON, JSONBuilder, JSONSink};
 pub use standard::{Standard, StandardBuilder, StandardSink};