Add option to ignore nested git repositories

This implements the suggestion made in #23 to provide an option to ignore nested
git repositories.

A nested git repository is identified by the presence of a .git file or
directory. It's a directory in the regular case, but it's a file for git
worktrees and git submodules.

This option is disabled by default.

crates/core/flags/complete/rg.zsh

@@ -146,6 +146,10 @@ _rg() {
     '--ignore-file-case-insensitive[process ignore files case insensitively]'
     $no'--no-ignore-file-case-insensitive[process ignore files case sensitively]'
 
+    + '(ignore-nested-git)' # Ignore nested git repository option
+    '--ignore-nested-git[ignore nested git repositories]'
+    $no"--no-ignore-nested-git[don't ignore nested git repositories]"
+
     + '(ignore-exclude)' # Local exclude (ignore)-file options
     "--no-ignore-exclude[don't respect local exclude (ignore) files]"
     $no'--ignore-exclude[respect local exclude (ignore) files]'

crates/core/flags/defs.rs

@@ -83,6 +83,7 @@ pub(super) const FLAGS: &[&dyn Flag] = &[
     &IgnoreCase,
     &IgnoreFile,
     &IgnoreFileCaseInsensitive,
+    &IgnoreNestedGit,
     &IncludeZero,
     &InvertMatch,
     &JSON,
@@ -3238,6 +3239,62 @@ fn test_ignore_file_case_insensitive() {
     assert_eq!(true, args.ignore_file_case_insensitive);
 }
 
+/// --ignore-nested-git
+#[derive(Debug)]
+struct IgnoreNestedGit;
+
+impl Flag for IgnoreNestedGit {
+    fn is_switch(&self) -> bool {
+        true
+    }
+    fn name_long(&self) -> &'static str {
+        "ignore-nested-git"
+    }
+    fn name_negated(&self) -> Option<&'static str> {
+        Some("no-ignore-nested-git")
+    }
+    fn doc_category(&self) -> Category {
+        Category::Filter
+    }
+    fn doc_short(&self) -> &'static str {
+        r"Ignore nested git repositories."
+    }
+    fn doc_long(&self) -> &'static str {
+        r"
+Ignore any nested directory containing a \fB.git\fP file or directory.
+This will prevent ripgrep from recursing into any git worktrees, submodules,
+or regular repositories.
+.sp
+Note that this does not affect top-level directories.
+"
+    }
+
+    fn update(&self, v: FlagValue, args: &mut LowArgs) -> anyhow::Result<()> {
+        args.ignore_nested_git = v.unwrap_switch();
+        Ok(())
+    }
+}
+
+#[cfg(test)]
+#[test]
+fn test_ignore_nested_git() {
+    let args = parse_low_raw(None::<&str>).unwrap();
+    assert_eq!(false, args.ignore_nested_git);
+
+    let args = parse_low_raw(["--ignore-nested-git"]).unwrap();
+    assert_eq!(true, args.ignore_nested_git);
+
+    let args =
+        parse_low_raw(["--ignore-nested-git", "--no-ignore-nested-git"])
+            .unwrap();
+    assert_eq!(false, args.ignore_nested_git);
+
+    let args =
+        parse_low_raw(["--no-ignore-nested-git", "--ignore-nested-git"])
+            .unwrap();
+    assert_eq!(true, args.ignore_nested_git);
+}
+
 /// --include-zero
 #[derive(Debug)]
 struct IncludeZero;

crates/core/flags/hiargs.rs

@@ -59,6 +59,7 @@ pub(crate) struct HiArgs {
     hyperlink_config: grep::printer::HyperlinkConfig,
     ignore_file_case_insensitive: bool,
     ignore_file: Vec<PathBuf>,
+    ignore_nested_git: bool,
     include_zero: bool,
     invert_match: bool,
     is_terminal_stdout: bool,
@@ -275,6 +276,7 @@ impl HiArgs {
             hyperlink_config,
             ignore_file: low.ignore_file,
             ignore_file_case_insensitive: low.ignore_file_case_insensitive,
+            ignore_nested_git: low.ignore_nested_git,
             include_zero: low.include_zero,
             invert_match: low.invert_match,
             is_terminal_stdout: state.is_terminal_stdout,
@@ -893,7 +895,8 @@ impl HiArgs {
             .git_ignore(!self.no_ignore_vcs)
             .git_exclude(!self.no_ignore_vcs && !self.no_ignore_exclude)
             .require_git(!self.no_require_git)
-            .ignore_case_insensitive(self.ignore_file_case_insensitive);
+            .ignore_case_insensitive(self.ignore_file_case_insensitive)
+            .ignore_nested_git_repo(self.ignore_nested_git);
         if !self.no_ignore_dot {
             builder.add_custom_ignore_filename(".rgignore");
         }

crates/core/flags/lowargs.rs

@@ -64,6 +64,7 @@ pub(crate) struct LowArgs {
     pub(crate) iglobs: Vec<String>,
     pub(crate) ignore_file: Vec<PathBuf>,
     pub(crate) ignore_file_case_insensitive: bool,
+    pub(crate) ignore_nested_git: bool,
     pub(crate) include_zero: bool,
     pub(crate) invert_match: bool,
     pub(crate) line_number: Option<bool>,

crates/ignore/src/dir.rs

@@ -46,6 +46,7 @@ enum IgnoreMatchInner<'a> {
     Gitignore(&'a gitignore::Glob),
     Types(types::Glob<'a>),
     Hidden,
+    NestedRepo,
 }
 
 impl<'a> IgnoreMatch<'a> {
@@ -64,6 +65,9 @@ impl<'a> IgnoreMatch<'a> {
     fn hidden() -> IgnoreMatch<'static> {
         IgnoreMatch(IgnoreMatchInner::Hidden)
     }
+    fn nested_repo() -> IgnoreMatch<'static> {
+        IgnoreMatch(IgnoreMatchInner::NestedRepo)
+    }
 }
 
 /// Options for the ignore matcher, shared between the matcher itself and the
@@ -84,6 +88,8 @@ struct IgnoreOptions {
     git_exclude: bool,
     /// Whether to ignore files case insensitively
     ignore_case_insensitive: bool,
+    /// Whether to ignore nested git repositories.
+    ignore_nested_git_repo: bool,
     /// Whether a git repository must be present in order to apply any
     /// git-related ignore rules.
     require_git: bool,
@@ -342,6 +348,7 @@ impl Ignore {
             || opts.git_global
             || opts.git_ignore
             || opts.git_exclude
+            || opts.ignore_nested_git_repo
             || has_custom_ignore_files
             || has_explicit_ignores
     }
@@ -422,6 +429,14 @@ impl Ignore {
             mut m_gi_exclude,
             mut m_explicit,
         ) = (Match::None, Match::None, Match::None, Match::None, Match::None);
+
+        if is_dir
+            && self.0.opts.ignore_nested_git_repo
+            && path.join(".git").exists()
+        {
+            return Match::Ignore(IgnoreMatch::nested_repo());
+        }
+
         let any_git =
             !self.0.opts.require_git || self.parents().any(|ig| ig.0.has_git);
         let mut saw_git = false;
@@ -599,6 +614,7 @@ impl IgnoreBuilder {
                 git_ignore: true,
                 git_exclude: true,
                 ignore_case_insensitive: false,
+                ignore_nested_git_repo: false,
                 require_git: true,
             },
         }
@@ -773,6 +789,17 @@ impl IgnoreBuilder {
         self.opts.ignore_case_insensitive = yes;
         self
     }
+
+    /// Enables ignoring nested git repositories.
+    ///
+    /// This is disabled by default.
+    pub(crate) fn ignore_nested_git_repo(
+        &mut self,
+        yes: bool,
+    ) -> &mut IgnoreBuilder {
+        self.opts.ignore_nested_git_repo = yes;
+        self
+    }
 }
 
 /// Creates a new gitignore matcher for the directory given.
@@ -887,6 +914,10 @@ mod tests {
         file.write_all(contents.as_bytes()).unwrap();
     }
 
+    fn rmfile<P: AsRef<Path>>(path: P) {
+        std::fs::remove_file(path).unwrap();
+    }
+
     fn mkdirp<P: AsRef<Path>>(path: P) {
         std::fs::create_dir_all(path).unwrap();
     }
@@ -1132,6 +1163,41 @@ mod tests {
         assert!(ig2.matched("bar", false).is_ignore());
     }
 
+    //
+    #[test]
+    fn ignore_nested_git() {
+        let td = tmpdir();
+        let repo = td.path().join("foo");
+        mkdirp(&repo);
+        let dotgit_path = repo.join(".git");
+        wfile(&dotgit_path, "");
+        wfile(repo.join("bar"), "");
+
+        let (ig_default, err) =
+            IgnoreBuilder::new().build().add_child(td.path());
+        assert!(err.is_none());
+
+        let (ig_git, err) = IgnoreBuilder::new()
+            .ignore_nested_git_repo(true)
+            .build()
+            .add_child(td.path());
+        assert!(err.is_none());
+
+        // is_dir = false, so no check for .git child
+        assert!(ig_git.matched(&repo, false).is_none());
+        // on the same level as .git; it's expected that the parent directory wouldn't be recursed in this case
+        assert!(ig_git.matched(repo.join("bar"), false).is_none());
+        // is_dir = true and has .git child
+        assert!(ig_git.matched(&repo, true).is_ignore());
+        // but by default, don't ignore dir with .git child
+        assert!(ig_default.matched(&repo, true).is_none());
+
+        // also test with .git as a directory
+        rmfile(&dotgit_path);
+        mkdirp(&dotgit_path);
+        assert!(ig_git.matched(&repo, true).is_ignore());
+    }
+
     #[test]
     fn absolute_parent() {
         let td = tmpdir();

crates/ignore/src/walk.rs

@@ -811,6 +811,14 @@ impl WalkBuilder {
         self
     }
 
+    /// Enables ignoring nested git repositories, including submodules.
+    ///
+    /// This is disabled by default.
+    pub fn ignore_nested_git_repo(&mut self, yes: bool) -> &mut WalkBuilder {
+        self.ig_builder.ignore_nested_git_repo(yes);
+        self
+    }
+
     /// Set a function for sorting directory entries by their path.
     ///
     /// If a compare function is set, the resulting iterator will return all