ignore: strip BOM

Fixes BurntSushi#2177

crates/ignore/Cargo.toml

@@ -28,6 +28,7 @@ regex = "1.1"
 same-file = "1.0.4"
 thread_local = "1"
 walkdir = "2.2.7"
+encoding_rs_io = "0.1.6"
 
 [target.'cfg(windows)'.dependencies.winapi-util]
 version = "0.1.2"

crates/ignore/src/gitignore.rs

@@ -15,6 +15,7 @@ use std::path::{Path, PathBuf};
 use std::str;
 use std::sync::Arc;
 
+use encoding_rs_io::DecodeReaderBytesBuilder;
 use globset::{Candidate, GlobBuilder, GlobSet, GlobSetBuilder};
 use regex::bytes::Regex;
 use thread_local::ThreadLocal;
@@ -389,7 +390,12 @@ impl GitignoreBuilder {
             Err(err) => return Some(Error::Io(err).with_path(path)),
             Ok(file) => file,
         };
-        let rdr = io::BufReader::new(file);
+        let rdr = io::BufReader::new(
+            DecodeReaderBytesBuilder::new()
+                .bom_sniffing(false)
+                .strip_bom(true)
+                .build(file),
+        );
         let mut errs = PartialErrorBuilder::default();
         for (i, line) in rdr.lines().enumerate() {
             let lineno = (i + 1) as u64;

crates/ignore/tests/bom_test.gitignore

@@ -0,0 +1 @@
+ignoreme

crates/ignore/tests/bom_test.rs

@@ -0,0 +1,23 @@
+use std::path::Path;
+
+use ignore::gitignore::{Gitignore, GitignoreBuilder};
+
+const IGNORE_FILE: &'static str = "tests/bom_test.gitignore";
+
+fn get_gitignore() -> Gitignore {
+    let mut builder = GitignoreBuilder::new("ROOT");
+    let error = builder.add(IGNORE_FILE);
+    assert!(error.is_none(), "failed to open gitignore file");
+    builder.build().unwrap()
+}
+
+// First entry should be ignored even when the ignore file starts with a BOM. See
+// https://github.com/BurntSushi/ripgrep/issues/2177
+#[test]
+fn test_match_first_entry() {
+    let gitignore = get_gitignore();
+    let path = "ignoreme";
+    assert!(gitignore
+        .matched_path_or_any_parents(Path::new(path), true)
+        .is_ignore());
+}