diff --git a/rust/hg-core/src/matchers.rs b/rust/hg-core/src/matchers.rs
--- a/rust/hg-core/src/matchers.rs
+++ b/rust/hg-core/src/matchers.rs
@@ -29,6 +29,7 @@
 use std::iter::FromIterator;
 use std::ops::Deref;
 use std::path::{Path, PathBuf};
+use crate::dirstate::status::IgnoreFnType;
 
 use micro_timer::timed;
 
@@ -246,7 +247,7 @@
 /// ```
 pub struct IncludeMatcher<'a> {
     patterns: Vec<u8>,
-    match_fn: Box<dyn for<'r> Fn(&'r HgPath) -> bool + 'a + Sync>,
+    match_fn: IgnoreFnType<'a>,
     /// Whether all the patterns match a prefix (i.e. recursively)
     prefix: bool,
     roots: HashSet<HgPathBuf>,
@@ -341,9 +342,9 @@
 
 /// Returns the regex pattern and a function that matches an `HgPath` against
 /// said regex formed by the given ignore patterns.
-fn build_regex_match(
-    ignore_patterns: &[IgnorePattern],
-) -> PatternResult<(Vec<u8>, Box<dyn Fn(&HgPath) -> bool + Sync>)> {
+fn build_regex_match<'a, 'b>(
+    ignore_patterns: &'a[IgnorePattern],
+) -> PatternResult<(Vec<u8>, IgnoreFnType<'b>)> {
     let mut regexps = vec![];
     let mut exact_set = HashSet::new();
 
@@ -365,10 +366,10 @@
         let func = move |filename: &HgPath| {
             exact_set.contains(filename) || matcher(filename)
         };
-        Box::new(func) as Box<dyn Fn(&HgPath) -> bool + Sync>
+        Box::new(func) as IgnoreFnType
     } else {
         let func = move |filename: &HgPath| exact_set.contains(filename);
-        Box::new(func) as Box<dyn Fn(&HgPath) -> bool + Sync>
+        Box::new(func) as IgnoreFnType
     };
 
     Ok((full_regex, func))
@@ -479,8 +480,8 @@
 /// should be matched.
 fn build_match<'a, 'b>(
     ignore_patterns: Vec<IgnorePattern>,
-) -> PatternResult<(Vec<u8>, Box<dyn Fn(&HgPath) -> bool + 'b + Sync>)> {
-    let mut match_funcs: Vec<Box<dyn Fn(&HgPath) -> bool + Sync>> = vec![];
+) -> PatternResult<(Vec<u8>, IgnoreFnType<'b>)> {
+    let mut match_funcs: Vec<IgnoreFnType<'b>> = vec![];
     // For debugging and printing
     let mut patterns = vec![];
 
@@ -563,14 +564,11 @@
 /// Parses all "ignore" files with their recursive includes and returns a
 /// function that checks whether a given file (in the general sense) should be
 /// ignored.
-pub fn get_ignore_function<'a>(
+pub fn get_ignore_matcher<'a>(
     mut all_pattern_files: Vec<PathBuf>,
     root_dir: &Path,
     inspect_pattern_bytes: &mut impl FnMut(&[u8]),
-) -> PatternResult<(
-    Box<dyn for<'r> Fn(&'r HgPath) -> bool + Sync + 'a>,
-    Vec<PatternFileWarning>,
-)> {
+) -> PatternResult<(IncludeMatcher<'a>, Vec<PatternFileWarning>)> {
     let mut all_patterns = vec![];
     let mut all_warnings = vec![];
 
@@ -593,10 +591,28 @@
         all_warnings.extend(warnings);
     }
     let matcher = IncludeMatcher::new(all_patterns)?;
-    Ok((
-        Box::new(move |path: &HgPath| matcher.matches(path)),
-        all_warnings,
-    ))
+    Ok((matcher, all_warnings))
+}
+
+/// Parses all "ignore" files with their recursive includes and returns a
+/// function that checks whether a given file (in the general sense) should be
+/// ignored.
+pub fn get_ignore_function<'a>(
+    all_pattern_files: Vec<PathBuf>,
+    root_dir: &Path,
+    inspect_pattern_bytes: &mut impl FnMut(&[u8]),
+) -> PatternResult<(
+    IgnoreFnType<'a>,
+    Vec<PatternFileWarning>,
+)> {
+    let res =
+        get_ignore_matcher(all_pattern_files, root_dir, inspect_pattern_bytes);
+    res.map(|(matcher, all_warnings)| {
+        let res: IgnoreFnType<'a> =
+            Box::new(move |path: &HgPath| matcher.matches(path));
+
+        (res, all_warnings)
+    })
 }
 
 impl<'a> IncludeMatcher<'a> {
@@ -631,6 +647,10 @@
             .chain(self.parents.iter());
         DirsChildrenMultiset::new(thing, Some(&self.parents))
     }
+
+    pub fn debug_get_patterns(&self) -> &[u8] {
+        self.patterns.as_ref()
+    }
 }
 
 impl<'a> Display for IncludeMatcher<'a> {
diff --git a/rust/rhg/src/commands/debugignorerhg.rs b/rust/rhg/src/commands/debugignorerhg.rs
new file mode 100644
--- /dev/null
+++ b/rust/rhg/src/commands/debugignorerhg.rs
@@ -0,0 +1,39 @@
+use crate::error::CommandError;
+use clap::SubCommand;
+use hg;
+use hg::matchers::get_ignore_matcher;
+use hg::StatusError;
+use log::warn;
+
+pub const HELP_TEXT: &str = "
+Show effective hgignore patterns used by rhg.
+
+This is a pure Rust version of `hg debugignore`.
+
+Some options might be missing, check the list below.
+";
+
+pub fn args() -> clap::App<'static, 'static> {
+    SubCommand::with_name("debugignorerhg").about(HELP_TEXT)
+}
+
+pub fn run(invocation: &crate::CliInvocation) -> Result<(), CommandError> {
+    let repo = invocation.repo?;
+
+    let ignore_file = repo.working_directory_vfs().join(".hgignore"); // TODO hardcoded
+
+    let (ignore_matcher, warnings) = get_ignore_matcher(
+        vec![ignore_file],
+        &repo.working_directory_path().to_owned(),
+        &mut |_pattern_bytes| (),
+    )
+    .map_err(|e| StatusError::from(e))?;
+
+    if !warnings.is_empty() {
+        warn!("Pattern warnings: {:?}", &warnings);
+    }
+
+    let patterns = ignore_matcher.debug_get_patterns();
+    println!("{}", String::from_utf8_lossy(patterns));
+    Ok(())
+}
diff --git a/rust/rhg/src/main.rs b/rust/rhg/src/main.rs
--- a/rust/rhg/src/main.rs
+++ b/rust/rhg/src/main.rs
@@ -465,6 +465,7 @@
     cat
     debugdata
     debugrequirements
+    debugignorerhg
     files
     root
     config