Be better with short circuiting with --quiet.

It didn't make sense for --quiet to be part of the printer, because --quiet
doesn't just mean "don't print," it also means, "stop after the first
match is found." This needs to be wired all the way up through directory
traversal, and it also needs to cause all of the search workers to quit
as well. We do it with an atomic that is only checked with --quiet is
given.

Fixes #116.

src/search_stream.rs

@@ -84,6 +84,7 @@ pub struct Options {
     pub eol: u8,
     pub invert_match: bool,
     pub line_number: bool,
+    pub quiet: bool,
     pub text: bool,
 }
 
@@ -97,6 +98,7 @@ impl Default for Options {
             eol: b'\n',
             invert_match: false,
             line_number: false,
+            quiet: false,
             text: false,
         }
     }
@@ -104,10 +106,16 @@ impl Default for Options {
 }
 
 impl Options {
-    /// Both --count and --files-with-matches options imply that we should not
-    /// display matches at all.
+    /// Several options (--quiet, --count, --files-with-matches) imply that
+    /// we shouldn't ever display matches.
     pub fn skip_matches(&self) -> bool {
-        return self.count || self.files_with_matches;
+        self.count || self.files_with_matches || self.quiet
+    }
+
+    /// Some options (--quiet, --files-with-matches) imply that we can stop
+    /// searching after the first match.
+    pub fn stop_after_first_match(&self) -> bool {
+        self.files_with_matches || self.quiet
     }
 }
 
@@ -197,6 +205,13 @@ impl<'a, R: io::Read, W: Terminal + Send> Searcher<'a, R, W> {
         self
     }
 
+    /// If enabled, don't show any output and quit searching after the first
+    /// match is found.
+    pub fn quiet(mut self, yes: bool) -> Self {
+        self.opts.quiet = yes;
+        self
+    }
+
     /// If enabled, search binary files as if they were text.
     pub fn text(mut self, yes: bool) -> Self {
         self.opts.text = yes;
@@ -265,8 +280,7 @@ impl<'a, R: io::Read, W: Terminal + Send> Searcher<'a, R, W> {
 
     #[inline(always)]
     fn terminate(&self) -> bool {
-        self.match_count > 0
-        && (self.printer.is_quiet() || self.opts.files_with_matches)
+        self.match_count > 0 && self.opts.stop_after_first_match()
     }
 
     #[inline(always)]