ripgrep: add --ignore-file-case-insensitive

The --ignore-file-case-insensitive flag causes all
.gitignore/.rgignore/.ignore files to have their globs matched without
regard for case. Because this introduces a potentially significant
performance regression, this is always disabled by default. Users that
need case insensitive matching can enable it on a case by case basis.

Closes #1164, Closes #1170

src/app.rs

@@ -571,6 +571,7 @@ pub fn all_args_and_flags() -> Vec<RGArg> {
     flag_iglob(&mut args);
     flag_ignore_case(&mut args);
     flag_ignore_file(&mut args);
+    flag_ignore_file_case_insensitive(&mut args);
     flag_invert_match(&mut args);
     flag_json(&mut args);
     flag_line_buffered(&mut args);
@@ -1209,6 +1210,27 @@ directly on the command line, then used -g instead.
     args.push(arg);
 }
 
+fn flag_ignore_file_case_insensitive(args: &mut Vec<RGArg>) {
+    const SHORT: &str =
+        "Process ignore files (.gitignore, .ignore, etc.) case insensitively.";
+    const LONG: &str = long!("\
+Process ignore files (.gitignore, .ignore, etc.) case insensitively. Note that
+this comes with a performance penalty and is most useful on case insensitive
+file systems (such as Windows).
+
+This flag can be disabled with the --no-ignore-file-case-insensitive flag.
+");
+    let arg = RGArg::switch("ignore-file-case-insensitive")
+        .help(SHORT).long_help(LONG)
+        .overrides("no-ignore-file-case-insensitive");
+    args.push(arg);
+
+    let arg = RGArg::switch("no-ignore-file-case-insensitive")
+        .hidden()
+        .overrides("ignore-file-case-insensitive");
+    args.push(arg);
+}
+
 fn flag_invert_match(args: &mut Vec<RGArg>) {
     const SHORT: &str = "Invert matching.";
     const LONG: &str = long!("\

src/args.rs

@@ -797,7 +797,8 @@ impl ArgMatches {
                 && !self.no_ignore_vcs()
                 && !self.no_ignore_global())
             .git_ignore(!self.no_ignore() && !self.no_ignore_vcs())
-            .git_exclude(!self.no_ignore() && !self.no_ignore_vcs());
+            .git_exclude(!self.no_ignore() && !self.no_ignore_vcs())
+            .ignore_case_insensitive(self.ignore_file_case_insensitive());
         if !self.no_ignore() {
             builder.add_custom_ignore_filename(".rgignore");
         }
@@ -1003,6 +1004,11 @@ impl ArgMatches {
         self.is_present("hidden") || self.unrestricted_count() >= 2
     }
 
+    /// Returns true if ignore files should be processed case insensitively.
+    fn ignore_file_case_insensitive(&self) -> bool {
+        self.is_present("ignore-file-case-insensitive")
+    }
+
     /// Return all of the ignore file paths given on the command line.
     fn ignore_paths(&self) -> Vec<PathBuf> {
         let paths = match self.values_of_os("ignore-file") {
@@ -1143,7 +1149,7 @@ impl ArgMatches {
             builder.add(&glob)?;
         }
         // This only enables case insensitivity for subsequent globs.
-        builder.case_insensitive(true)?;
+        builder.case_insensitive(true).unwrap();
         for glob in self.values_of_lossy_vec("iglob") {
             builder.add(&glob)?;
         }