binary: rejigger ripgrep's handling of binary files

This commit attempts to surface binary filtering in a slightly more
user friendly way. Namely, before, ripgrep would silently stop
searching a file if it detected a NUL byte, even if it had previously
printed a match. This can lead to the user quite reasonably assuming
that there are no more matches, since a partial search is fairly
unintuitive. (ripgrep has this behavior by default because it really
wants to NOT search binary files at all, just like it doesn't search
gitignored or hidden files.)

With this commit, if a match has already been printed and ripgrep detects
a NUL byte, then it will print a warning message indicating that the search
stopped prematurely.

Moreover, this commit adds a new flag, --binary, which causes ripgrep to
stop filtering binary files, but in a way that still avoids dumping
binary data into terminals. That is, the --binary flag makes ripgrep
behave more like grep's default behavior.

For files explicitly specified in a search, e.g., `rg foo some-file`,
then no binary filtering is applied (just like no gitignore and no
hidden file filtering is applied). Instead, ripgrep behaves as if you
gave the --binary flag for all explicitly given files.

This was a fairly invasive change, and potentially increases the UX
complexity of ripgrep around binary files. (Before, there were two
binary modes, where as now there are three.) However, ripgrep is now a
bit louder with warning messages when binary file detection might
otherwise be hiding potential matches, so hopefully this is a net
improvement.

Finally, the `-uuu` convenience now maps to `--no-ignore --hidden
--binary`, since this is closer to the actualy intent of the
`--unrestricted` flag, i.e., to reduce ripgrep's smart filtering. As a
consequence, `rg -uuu foo` should now search roughly the same number of
bytes as `grep -r foo`, and `rg -uuua foo` should search roughly the
same number of bytes as `grep -ra foo`. (The "roughly" weasel word is
used because grep's and ripgrep's binary file detection might differ
somewhat---perhaps based on buffer sizes---which can impact exactly what
is and isn't searched.)

See the numerous tests in tests/binary.rs for intended behavior.

Fixes #306, Fixes #855

src/search.rs

@@ -10,7 +10,7 @@ use grep::matcher::Matcher;
 use grep::pcre2::{RegexMatcher as PCRE2RegexMatcher};
 use grep::printer::{JSON, Standard, Summary, Stats};
 use grep::regex::{RegexMatcher as RustRegexMatcher};
-use grep::searcher::Searcher;
+use grep::searcher::{BinaryDetection, Searcher};
 use ignore::overrides::Override;
 use serde_json as json;
 use serde_json::json;
@@ -27,6 +27,8 @@ struct Config {
     preprocessor: Option<PathBuf>,
     preprocessor_globs: Override,
     search_zip: bool,
+    binary_implicit: BinaryDetection,
+    binary_explicit: BinaryDetection,
 }
 
 impl Default for Config {
@@ -36,6 +38,8 @@ impl Default for Config {
             preprocessor: None,
             preprocessor_globs: Override::empty(),
             search_zip: false,
+            binary_implicit: BinaryDetection::none(),
+            binary_explicit: BinaryDetection::none(),
         }
     }
 }
@@ -134,6 +138,37 @@ impl SearchWorkerBuilder {
         self.config.search_zip = yes;
         self
     }
+
+    /// Set the binary detection that should be used when searching files
+    /// found via a recursive directory search.
+    ///
+    /// Generally, this binary detection may be `BinaryDetection::quit` if
+    /// we want to skip binary files completely.
+    ///
+    /// By default, no binary detection is performed.
+    pub fn binary_detection_implicit(
+        &mut self,
+        detection: BinaryDetection,
+    ) -> &mut SearchWorkerBuilder {
+        self.config.binary_implicit = detection;
+        self
+    }
+
+    /// Set the binary detection that should be used when searching files
+    /// explicitly supplied by an end user.
+    ///
+    /// Generally, this binary detection should NOT be `BinaryDetection::quit`,
+    /// since we never want to automatically filter files supplied by the end
+    /// user.
+    ///
+    /// By default, no binary detection is performed.
+    pub fn binary_detection_explicit(
+        &mut self,
+        detection: BinaryDetection,
+    ) -> &mut SearchWorkerBuilder {
+        self.config.binary_explicit = detection;
+        self
+    }
 }
 
 /// The result of executing a search.
@@ -308,6 +343,14 @@ impl<W: WriteColor> SearchWorker<W> {
 
     /// Search the given subject using the appropriate strategy.
     fn search_impl(&mut self, subject: &Subject) -> io::Result<SearchResult> {
+        let bin =
+            if subject.is_explicit() {
+                self.config.binary_explicit.clone()
+            } else {
+                self.config.binary_implicit.clone()
+            };
+        self.searcher.set_binary_detection(bin);
+
         let path = subject.path();
         if subject.is_stdin() {
             let stdin = io::stdin();