cli: add --no-ignore-exclude flag

This commit adds a new --no-ignore-exclude flag that permits disabling
the use of .git/info/exclude filtering. Local exclusions are manual
configurations to a repository and are not shared, so it is sometimes
useful to disable to get a consistent view of a repository.

This also adds a new section to the man page that describes automatic
filtering.

Closes #1420

src/app.rs

@@ -595,6 +595,7 @@ pub fn all_args_and_flags() -> Vec<RGArg> {
     flag_no_config(&mut args);
     flag_no_ignore(&mut args);
     flag_no_ignore_dot(&mut args);
+    flag_no_ignore_exclude(&mut args);
     flag_no_ignore_global(&mut args);
     flag_no_ignore_messages(&mut args);
     flag_no_ignore_parent(&mut args);
@@ -1769,6 +1770,26 @@ This flag can be disabled with the --ignore-dot flag.
     args.push(arg);
 }
 
+fn flag_no_ignore_exclude(args: &mut Vec<RGArg>) {
+    const SHORT: &str = "Don't respect local exclusion files.";
+    const LONG: &str = long!("\
+Don't respect ignore files that are manually configured for the repository
+such as git's '.git/info/exclude'.
+
+This flag can be disabled with the --ignore-exclude flag.
+");
+    let arg = RGArg::switch("no-ignore-exclude")
+        .help(SHORT).long_help(LONG)
+        .overrides("ignore-exclude");
+    args.push(arg);
+
+    let arg = RGArg::switch("ignore-exclude")
+        .hidden()
+        .overrides("no-ignore-exclude");
+    args.push(arg);
+}
+
+
 fn flag_no_ignore_global(args: &mut Vec<RGArg>) {
     const SHORT: &str = "Don't respect global ignore files.";
     const LONG: &str = long!("\

src/args.rs

@@ -881,7 +881,7 @@ impl ArgMatches {
             .ignore(!self.no_ignore_dot())
             .git_global(!self.no_ignore_vcs() && !self.no_ignore_global())
             .git_ignore(!self.no_ignore_vcs())
-            .git_exclude(!self.no_ignore_vcs())
+            .git_exclude(!self.no_ignore_vcs() && !self.no_ignore_exclude())
             .ignore_case_insensitive(self.ignore_file_case_insensitive());
         if !self.no_ignore() {
             builder.add_custom_ignore_filename(".rgignore");
@@ -1231,6 +1231,11 @@ impl ArgMatches {
         self.is_present("no-ignore-dot") || self.no_ignore()
     }
 
+    /// Returns true if local exclude (ignore) files should be ignored.
+    fn no_ignore_exclude(&self) -> bool {
+        self.is_present("no-ignore-exclude") || self.no_ignore()
+    }
+
     /// Returns true if global ignore files should be ignored.
     fn no_ignore_global(&self) -> bool {
         self.is_present("no-ignore-global") || self.no_ignore()