Lots of progress:

- Refactored interaction between CLI args and rest of xrep.
  - Filling in a lot more options, including file type filtering.
  - Fixing some bugs in globbing/ignoring.
  - More documentation.

src/out.rs

@@ -0,0 +1,45 @@
+use std::io::{self, Write};
+
+/// Out controls the actual output of all search results for a particular file
+/// to the end user.
+///
+/// (The difference between Out and Printer is that a Printer works with
+/// individual search results where as Out works with search results for each
+/// file as a whole. For example, it knows when to print a file separator.)
+pub struct Out<W: io::Write> {
+    wtr: io::BufWriter<W>,
+    printed: bool,
+    file_separator: Vec<u8>,
+}
+
+impl<W: io::Write> Out<W> {
+    /// Create a new Out that writes to the wtr given.
+    pub fn new(wtr: W) -> Out<W> {
+        Out {
+            wtr: io::BufWriter::new(wtr),
+            printed: false,
+            file_separator: vec![],
+        }
+    }
+
+    /// If set, the separator is printed between matches from different files.
+    /// By default, no separator is printed.
+    ///
+    /// If sep is empty, then no file separator is printed.
+    pub fn file_separator(mut self, sep: Vec<u8>) -> Out<W> {
+        self.file_separator = sep;
+        self
+    }
+
+    /// Write the search results of a single file to the underlying wtr and
+    /// flush wtr.
+    pub fn write(&mut self, buf: &[u8]) {
+        if self.printed && !self.file_separator.is_empty() {
+            let _ = self.wtr.write_all(&self.file_separator);
+            let _ = self.wtr.write_all(b"\n");
+        }
+        let _ = self.wtr.write_all(buf);
+        let _ = self.wtr.flush();
+        self.printed = true;
+    }
+}