Merge branch 'master' into cursor-shape-new

13 files changed, 1142 insertions, 181 deletions

diff --git a/helix-core/src/auto_pairs.rs b/helix-core/src/auto_pairs.rs
index cc966852..c037afef 100644
--- a/helix-core/src/auto_pairs.rs
+++ b/helix-core/src/auto_pairs.rs
@@ -2,6 +2,7 @@
 //! this module provides the functionality to insert the paired closing character.
 
 use crate::{Range, Rope, Selection, Tendril, Transaction};
+use log::debug;
 use smallvec::SmallVec;
 
 // Heavily based on https://github.com/codemirror/closebrackets/
@@ -15,7 +16,9 @@ pub const PAIRS: &[(char, char)] = &[
     ('`', '`'),
 ];
 
-const CLOSE_BEFORE: &str = ")]}'\":;> \n\r\u{000B}\u{000C}\u{0085}\u{2028}\u{2029}"; // includes space and newlines
+// [TODO] build this dynamically in language config. see #992
+const OPEN_BEFORE: &str = "([{'\":;,> \n\r\u{000B}\u{000C}\u{0085}\u{2028}\u{2029}";
+const CLOSE_BEFORE: &str = ")]}'\":;,> \n\r\u{000B}\u{000C}\u{0085}\u{2028}\u{2029}"; // includes space and newlines
 
 // insert hook:
 // Fn(doc, selection, char) => Option<Transaction>
@@ -25,40 +28,44 @@ const CLOSE_BEFORE: &str = ")]}'\":;> \n\r\u{000B}\u{000C}\u{0085}\u{2028}\u{202
 //
 // to simplify, maybe return Option<Transaction> and just reimplement the default
 
-// TODO: delete implementation where it erases the whole bracket (|) -> |
+// [TODO]
+// * delete implementation where it erases the whole bracket (|) -> |
+// * do not reduce to cursors; use whole selections, and surround with pair
+// * change to multi character pairs to handle cases like placing the cursor in the
+//   middle of triple quotes, and more exotic pairs like Jinja's {% %}
 
 #[must_use]
 pub fn hook(doc: &Rope, selection: &Selection, ch: char) -> Option<Transaction> {
+    debug!("autopairs hook selection: {:#?}", selection);
+
+    let cursors = selection.clone().cursors(doc.slice(..));
+
     for &(open, close) in PAIRS {
         if open == ch {
             if open == close {
-                return handle_same(doc, selection, open);
+                return Some(handle_same(doc, &cursors, open, CLOSE_BEFORE, OPEN_BEFORE));
             } else {
-                return Some(handle_open(doc, selection, open, close, CLOSE_BEFORE));
+                return Some(handle_open(doc, &cursors, open, close, CLOSE_BEFORE));
             }
         }
 
         if close == ch {
             // && char_at pos == close
-            return Some(handle_close(doc, selection, open, close));
+            return Some(handle_close(doc, &cursors, open, close));
         }
     }
 
     None
 }
 
-// TODO: special handling for lifetimes in rust: if preceeded by & or < don't auto close '
-// for example "&'a mut", or "fn<'a>"
-
-fn next_char(doc: &Rope, pos: usize) -> Option<char> {
-    if pos >= doc.len_chars() {
+fn prev_char(doc: &Rope, pos: usize) -> Option<char> {
+    if pos == 0 {
         return None;
     }
-    Some(doc.char(pos))
+
+    doc.get_char(pos - 1)
 }
-// TODO: selections should be extended if range, moved if point.
 
-// TODO: if not cursor but selection, wrap on both sides of selection (surround)
 fn handle_open(
     doc: &Rope,
     selection: &Selection,
@@ -66,98 +73,362 @@ fn handle_open(
     close: char,
     close_before: &str,
 ) -> Transaction {
-    let mut ranges = SmallVec::with_capacity(selection.len());
+    let mut end_ranges = SmallVec::with_capacity(selection.len());
 
     let mut offs = 0;
 
-    let transaction = Transaction::change_by_selection(doc, selection, |range| {
-        let pos = range.head;
-        let next = next_char(doc, pos);
+    let transaction = Transaction::change_by_selection(doc, selection, |start_range| {
+        let start_head = start_range.head;
 
-        let head = pos + offs + open.len_utf8();
-        // if selection, retain anchor, if cursor, move over
-        ranges.push(Range::new(
-            if range.is_empty() {
-                head
-            } else {
-                range.anchor + offs
-            },
-            head,
-        ));
+        let next = doc.get_char(start_head);
+        let end_head = start_head + offs + open.len_utf8();
+
+        let end_anchor = if start_range.is_empty() {
+            end_head
+        } else {
+            start_range.anchor + offs
+        };
+
+        end_ranges.push(Range::new(end_anchor, end_head));
 
         match next {
             Some(ch) if !close_before.contains(ch) => {
-                offs += 1;
-                // TODO: else return (use default handler that inserts open)
-                (pos, pos, Some(Tendril::from_char(open)))
+                offs += open.len_utf8();
+                (start_head, start_head, Some(Tendril::from_char(open)))
             }
             // None | Some(ch) if close_before.contains(ch) => {}
             _ => {
                 // insert open & close
-                let mut pair = Tendril::with_capacity(2);
-                pair.push_char(open);
-                pair.push_char(close);
-
-                offs += 2;
-
-                (pos, pos, Some(pair))
+                let pair = Tendril::from_iter([open, close]);
+                offs += open.len_utf8() + close.len_utf8();
+                (start_head, start_head, Some(pair))
             }
         }
     });
 
-    transaction.with_selection(Selection::new(ranges, selection.primary_index()))
+    let t = transaction.with_selection(Selection::new(end_ranges, selection.primary_index()));
+    debug!("auto pair transaction: {:#?}", t);
+    t
 }
 
 fn handle_close(doc: &Rope, selection: &Selection, _open: char, close: char) -> Transaction {
-    let mut ranges = SmallVec::with_capacity(selection.len());
+    let mut end_ranges = SmallVec::with_capacity(selection.len());
 
     let mut offs = 0;
 
-    let transaction = Transaction::change_by_selection(doc, selection, |range| {
-        let pos = range.head;
-        let next = next_char(doc, pos);
+    let transaction = Transaction::change_by_selection(doc, selection, |start_range| {
+        let start_head = start_range.head;
+        let next = doc.get_char(start_head);
+        let end_head = start_head + offs + close.len_utf8();
 
-        let head = pos + offs + close.len_utf8();
-        // if selection, retain anchor, if cursor, move over
-        ranges.push(Range::new(
-            if range.is_empty() {
-                head
-            } else {
-                range.anchor + offs
-            },
-            head,
-        ));
+        let end_anchor = if start_range.is_empty() {
+            end_head
+        } else {
+            start_range.anchor + offs
+        };
+
+        end_ranges.push(Range::new(end_anchor, end_head));
 
         if next == Some(close) {
-            //  return transaction that moves past close
-            (pos, pos, None) // no-op
+            // return transaction that moves past close
+            (start_head, start_head, None) // no-op
         } else {
             offs += close.len_utf8();
+            (start_head, start_head, Some(Tendril::from_char(close)))
+        }
+    });
+
+    transaction.with_selection(Selection::new(end_ranges, selection.primary_index()))
+}
 
-            // TODO: else return (use default handler that inserts close)
-            (pos, pos, Some(Tendril::from_char(close)))
+/// handle cases where open and close is the same, or in triples ("""docstring""")
+fn handle_same(
+    doc: &Rope,
+    selection: &Selection,
+    token: char,
+    close_before: &str,
+    open_before: &str,
+) -> Transaction {
+    let mut end_ranges = SmallVec::with_capacity(selection.len());
+
+    let mut offs = 0;
+
+    let transaction = Transaction::change_by_selection(doc, selection, |start_range| {
+        let start_head = start_range.head;
+        let end_head = start_head + offs + token.len_utf8();
+
+        // if selection, retain anchor, if cursor, move over
+        let end_anchor = if start_range.is_empty() {
+            end_head
+        } else {
+            start_range.anchor + offs
+        };
+
+        end_ranges.push(Range::new(end_anchor, end_head));
+
+        let next = doc.get_char(start_head);
+        let prev = prev_char(doc, start_head);
+
+        if next == Some(token) {
+            //  return transaction that moves past close
+            (start_head, start_head, None) // no-op
+        } else {
+            let mut pair = Tendril::with_capacity(2 * token.len_utf8() as u32);
+            pair.push_char(token);
+
+            // for equal pairs, don't insert both open and close if either
+            // side has a non-pair char
+            if (next.is_none() || close_before.contains(next.unwrap()))
+                && (prev.is_none() || open_before.contains(prev.unwrap()))
+            {
+                pair.push_char(token);
+            }
+
+            offs += pair.len();
+            (start_head, start_head, Some(pair))
         }
     });
 
-    transaction.with_selection(Selection::new(ranges, selection.primary_index()))
+    transaction.with_selection(Selection::new(end_ranges, selection.primary_index()))
 }
 
-// handle cases where open and close is the same, or in triples ("""docstring""")
-fn handle_same(_doc: &Rope, _selection: &Selection, _token: char) -> Option<Transaction> {
-    // if not cursor but selection, wrap
-    // let next = next char
-
-    // if next == bracket {
-    //   // if start of syntax node, insert token twice (new pair because node is complete)
-    //   // elseif colsedBracketAt
-    //      // is_triple == allow triple && next 3 is equal
-    //      // cursor jump over
-    // }
-    //} else if allow_triple && followed by triple {
-    //}
-    //} else if next != word char && prev != bracket && prev != word char {
-    // // condition checks for cases like I' where you don't want I'' (or I'm)
-    //  insert pair ("")
-    //}
-    None
+#[cfg(test)]
+mod test {
+    use super::*;
+    use smallvec::smallvec;
+
+    fn differing_pairs() -> impl Iterator<Item = &'static (char, char)> {
+        PAIRS.iter().filter(|(open, close)| open != close)
+    }
+
+    fn matching_pairs() -> impl Iterator<Item = &'static (char, char)> {
+        PAIRS.iter().filter(|(open, close)| open == close)
+    }
+
+    fn test_hooks(
+        in_doc: &Rope,
+        in_sel: &Selection,
+        ch: char,
+        expected_doc: &Rope,
+        expected_sel: &Selection,
+    ) {
+        let trans = hook(&in_doc, &in_sel, ch).unwrap();
+        let mut actual_doc = in_doc.clone();
+        assert!(trans.apply(&mut actual_doc));
+        assert_eq!(expected_doc, &actual_doc);
+        assert_eq!(expected_sel, trans.selection().unwrap());
+    }
+
+    fn test_hooks_with_pairs<I, F, R>(
+        in_doc: &Rope,
+        in_sel: &Selection,
+        pairs: I,
+        get_expected_doc: F,
+        actual_sel: &Selection,
+    ) where
+        I: IntoIterator<Item = &'static (char, char)>,
+        F: Fn(char, char) -> R,
+        R: Into<Rope>,
+        Rope: From<R>,
+    {
+        pairs.into_iter().for_each(|(open, close)| {
+            test_hooks(
+                in_doc,
+                in_sel,
+                *open,
+                &Rope::from(get_expected_doc(*open, *close)),
+                actual_sel,
+            )
+        });
+    }
+
+    // [] indicates range
+
+    /// [] -> insert ( -> ([])
+    #[test]
+    fn test_insert_blank() {
+        test_hooks_with_pairs(
+            &Rope::new(),
+            &Selection::single(1, 0),
+            PAIRS,
+            |open, close| format!("{}{}", open, close),
+            &Selection::single(1, 1),
+        );
+    }
+
+    /// []              ([])
+    /// [] -> insert -> ([])
+    /// []              ([])
+    #[test]
+    fn test_insert_blank_multi_cursor() {
+        test_hooks_with_pairs(
+            &Rope::from("\n\n\n"),
+            &Selection::new(
+                smallvec!(Range::new(1, 0), Range::new(2, 1), Range::new(3, 2),),
+                0,
+            ),
+            PAIRS,
+            |open, close| {
+                format!(
+                    "{open}{close}\n{open}{close}\n{open}{close}\n",
+                    open = open,
+                    close = close
+                )
+            },
+            &Selection::new(
+                smallvec!(Range::point(1), Range::point(4), Range::point(7),),
+                0,
+            ),
+        );
+    }
+
+    // [TODO] broken until it works with selections
+    /// fo[o] -> append ( -> fo[o(])
+    #[ignore]
+    #[test]
+    fn test_append() {
+        test_hooks_with_pairs(
+            &Rope::from("foo"),
+            &Selection::single(2, 4),
+            PAIRS,
+            |open, close| format!("foo{}{}", open, close),
+            &Selection::single(2, 5),
+        );
+    }
+
+    /// ([]) -> insert ) -> ()[]
+    #[test]
+    fn test_insert_close_inside_pair() {
+        for (open, close) in PAIRS {
+            let doc = Rope::from(format!("{}{}", open, close));
+
+            test_hooks(
+                &doc,
+                &Selection::single(2, 1),
+                *close,
+                &doc,
+                &Selection::point(2),
+            );
+        }
+    }
+
+    /// ([])                ()[]
+    /// ([]) -> insert ) -> ()[]
+    /// ([])                ()[]
+    #[test]
+    fn test_insert_close_inside_pair_multi_cursor() {
+        let sel = Selection::new(
+            smallvec!(Range::new(2, 1), Range::new(5, 4), Range::new(8, 7),),
+            0,
+        );
+
+        let expected_sel = Selection::new(
+            // smallvec!(Range::new(3, 2), Range::new(6, 5), Range::new(9, 8),),
+            smallvec!(Range::point(2), Range::point(5), Range::point(8),),
+            0,
+        );
+
+        for (open, close) in PAIRS {
+            let doc = Rope::from(format!(
+                "{open}{close}\n{open}{close}\n{open}{close}\n",
+                open = open,
+                close = close
+            ));
+
+            test_hooks(&doc, &sel, *close, &doc, &expected_sel);
+        }
+    }
+
+    /// ([]) -> insert ( -> (([]))
+    #[test]
+    fn test_insert_open_inside_pair() {
+        let sel = Selection::single(2, 1);
+        let expected_sel = Selection::point(2);
+
+        for (open, close) in differing_pairs() {
+            let doc = Rope::from(format!("{}{}", open, close));
+            let expected_doc = Rope::from(format!(
+                "{open}{open}{close}{close}",
+                open = open,
+                close = close
+            ));
+
+            test_hooks(&doc, &sel, *open, &expected_doc, &expected_sel);
+        }
+    }
+
+    /// ([]) -> insert " -> ("[]")
+    #[test]
+    fn test_insert_nested_open_inside_pair() {
+        let sel = Selection::single(2, 1);
+        let expected_sel = Selection::point(2);
+
+        for (outer_open, outer_close) in differing_pairs() {
+            let doc = Rope::from(format!("{}{}", outer_open, outer_close,));
+
+            for (inner_open, inner_close) in matching_pairs() {
+                let expected_doc = Rope::from(format!(
+                    "{}{}{}{}",
+                    outer_open, inner_open, inner_close, outer_close
+                ));
+
+                test_hooks(&doc, &sel, *inner_open, &expected_doc, &expected_sel);
+            }
+        }
+    }
+
+    /// []word -> insert ( -> ([]word
+    #[test]
+    fn test_insert_open_before_non_pair() {
+        test_hooks_with_pairs(
+            &Rope::from("word"),
+            &Selection::single(1, 0),
+            PAIRS,
+            |open, _| format!("{}word", open),
+            &Selection::point(1),
+        )
+    }
+
+    // [TODO] broken until it works with selections
+    /// [wor]d -> insert ( -> ([wor]d
+    #[test]
+    #[ignore]
+    fn test_insert_open_with_selection() {
+        test_hooks_with_pairs(
+            &Rope::from("word"),
+            &Selection::single(0, 4),
+            PAIRS,
+            |open, _| format!("{}word", open),
+            &Selection::single(1, 5),
+        )
+    }
+
+    /// we want pairs that are *not* the same char to be inserted after
+    /// a non-pair char, for cases like functions, but for pairs that are
+    /// the same char, we want to *not* insert a pair to handle cases like "I'm"
+    ///
+    /// word[]  -> insert ( -> word([])
+    /// word[]  -> insert ' -> word'[]
+    #[test]
+    fn test_insert_open_after_non_pair() {
+        let doc = Rope::from("word");
+        let sel = Selection::single(5, 4);
+        let expected_sel = Selection::point(5);
+
+        test_hooks_with_pairs(
+            &doc,
+            &sel,
+            differing_pairs(),
+            |open, close| format!("word{}{}", open, close),
+            &expected_sel,
+        );
+
+        test_hooks_with_pairs(
+            &doc,
+            &sel,
+            matching_pairs(),
+            |open, _| format!("word{}", open),
+            &expected_sel,
+        );
+    }
 }
diff --git a/helix-core/src/diagnostic.rs b/helix-core/src/diagnostic.rs
index ad1ba16a..4fcf51c9 100644
--- a/helix-core/src/diagnostic.rs
+++ b/helix-core/src/diagnostic.rs
@@ -1,7 +1,7 @@
 //! LSP diagnostic utility types.
 
 /// Describes the severity level of a [`Diagnostic`].
-#[derive(Debug, Eq, PartialEq)]
+#[derive(Debug, Clone, Copy, Eq, PartialEq)]
 pub enum Severity {
     Error,
     Warning,
@@ -17,7 +17,7 @@ pub struct Range {
 }
 
 /// Corresponds to [`lsp_types::Diagnostic`](https://docs.rs/lsp-types/0.91.0/lsp_types/struct.Diagnostic.html)
-#[derive(Debug)]
+#[derive(Debug, Clone)]
 pub struct Diagnostic {
     pub range: Range,
     pub line: usize,
diff --git a/helix-core/src/increment/date_time.rs b/helix-core/src/increment/date_time.rs
new file mode 100644
index 00000000..e3cfe107
--- /dev/null
+++ b/helix-core/src/increment/date_time.rs
@@ -0,0 +1,490 @@
+use chrono::{Datelike, Duration, NaiveDate, NaiveDateTime, NaiveTime, Timelike};
+use once_cell::sync::Lazy;
+use regex::Regex;
+use ropey::RopeSlice;
+
+use std::borrow::Cow;
+use std::cmp;
+
+use super::Increment;
+use crate::{Range, Tendril};
+
+#[derive(Debug, PartialEq, Eq)]
+pub struct DateTimeIncrementor {
+    date_time: NaiveDateTime,
+    range: Range,
+    fmt: &'static str,
+    field: DateField,
+}
+
+impl DateTimeIncrementor {
+    pub fn from_range(text: RopeSlice, range: Range) -> Option<DateTimeIncrementor> {
+        let range = if range.is_empty() {
+            if range.anchor < text.len_chars() {
+                // Treat empty range as a cursor range.
+                range.put_cursor(text, range.anchor + 1, true)
+            } else {
+                // The range is empty and at the end of the text.
+                return None;
+            }
+        } else {
+            range
+        };
+
+        FORMATS.iter().find_map(|format| {
+            let from = range.from().saturating_sub(format.max_len);
+            let to = (range.from() + format.max_len).min(text.len_chars());
+
+            let (from_in_text, to_in_text) = (range.from() - from, range.to() - from);
+            let text: Cow<str> = text.slice(from..to).into();
+
+            let captures = format.regex.captures(&text)?;
+            if captures.len() - 1 != format.fields.len() {
+                return None;
+            }
+
+            let date_time = captures.get(0)?;
+            let offset = range.from() - from_in_text;
+            let range = Range::new(date_time.start() + offset, date_time.end() + offset);
+
+            let field = captures
+                .iter()
+                .skip(1)
+                .enumerate()
+                .find_map(|(i, capture)| {
+                    let capture = capture?;
+                    let capture_range = capture.range();
+
+                    if capture_range.contains(&from_in_text)
+                        && capture_range.contains(&(to_in_text - 1))
+                    {
+                        Some(format.fields[i])
+                    } else {
+                        None
+                    }
+                })?;
+
+            let has_date = format.fields.iter().any(|f| f.unit.is_date());
+            let has_time = format.fields.iter().any(|f| f.unit.is_time());
+
+            let date_time = &text[date_time.start()..date_time.end()];
+            let date_time = match (has_date, has_time) {
+                (true, true) => NaiveDateTime::parse_from_str(date_time, format.fmt).ok()?,
+                (true, false) => {
+                    let date = NaiveDate::parse_from_str(date_time, format.fmt).ok()?;
+
+                    date.and_hms(0, 0, 0)
+                }
+                (false, true) => {
+                    let time = NaiveTime::parse_from_str(date_time, format.fmt).ok()?;
+
+                    NaiveDate::from_ymd(0, 1, 1).and_time(time)
+                }
+                (false, false) => return None,
+            };
+
+            Some(DateTimeIncrementor {
+                date_time,
+                range,
+                fmt: format.fmt,
+                field,
+            })
+        })
+    }
+}
+
+impl Increment for DateTimeIncrementor {
+    fn increment(&self, amount: i64) -> (Range, Tendril) {
+        let date_time = match self.field.unit {
+            DateUnit::Years => add_years(self.date_time, amount),
+            DateUnit::Months => add_months(self.date_time, amount),
+            DateUnit::Days => add_duration(self.date_time, Duration::days(amount)),
+            DateUnit::Hours => add_duration(self.date_time, Duration::hours(amount)),
+            DateUnit::Minutes => add_duration(self.date_time, Duration::minutes(amount)),
+            DateUnit::Seconds => add_duration(self.date_time, Duration::seconds(amount)),
+            DateUnit::AmPm => toggle_am_pm(self.date_time),
+        }
+        .unwrap_or(self.date_time);
+
+        (self.range, date_time.format(self.fmt).to_string().into())
+    }
+}
+
+static FORMATS: Lazy<Vec<Format>> = Lazy::new(|| {
+    vec![
+        Format::new("%Y-%m-%d %H:%M:%S"), // 2021-11-24 07:12:23
+        Format::new("%Y/%m/%d %H:%M:%S"), // 2021/11/24 07:12:23
+        Format::new("%Y-%m-%d %H:%M"),    // 2021-11-24 07:12
+        Format::new("%Y/%m/%d %H:%M"),    // 2021/11/24 07:12
+        Format::new("%Y-%m-%d"),          // 2021-11-24
+        Format::new("%Y/%m/%d"),          // 2021/11/24
+        Format::new("%a %b %d %Y"),       // Wed Nov 24 2021
+        Format::new("%d-%b-%Y"),          // 24-Nov-2021
+        Format::new("%Y %b %d"),          // 2021 Nov 24
+        Format::new("%b %d, %Y"),         // Nov 24, 2021
+        Format::new("%-I:%M:%S %P"),      // 7:21:53 am
+        Format::new("%-I:%M %P"),         // 7:21 am
+        Format::new("%-I:%M:%S %p"),      // 7:21:53 AM
+        Format::new("%-I:%M %p"),         // 7:21 AM
+        Format::new("%H:%M:%S"),          // 23:24:23
+        Format::new("%H:%M"),             // 23:24
+    ]
+});
+
+#[derive(Debug)]
+struct Format {
+    fmt: &'static str,
+    fields: Vec<DateField>,
+    regex: Regex,
+    max_len: usize,
+}
+
+impl Format {
+    fn new(fmt: &'static str) -> Self {
+        let mut remaining = fmt;
+        let mut fields = Vec::new();
+        let mut regex = String::new();
+        let mut max_len = 0;
+
+        while let Some(i) = remaining.find('%') {
+            let after = &remaining[i + 1..];
+            let mut chars = after.chars();
+            let c = chars.next().unwrap();
+
+            let spec_len = if c == '-' {
+                1 + chars.next().unwrap().len_utf8()
+            } else {
+                c.len_utf8()
+            };
+
+            let specifier = &after[..spec_len];
+            let field = DateField::from_specifier(specifier).unwrap();
+            fields.push(field);
+            max_len += field.max_len + remaining[..i].len();
+            regex += &remaining[..i];
+            regex += &format!("({})", field.regex);
+            remaining = &after[spec_len..];
+        }
+
+        let regex = Regex::new(&regex).unwrap();
+
+        Self {
+            fmt,
+            fields,
+            regex,
+            max_len,
+        }
+    }
+}
+
+impl PartialEq for Format {
+    fn eq(&self, other: &Self) -> bool {
+        self.fmt == other.fmt && self.fields == other.fields && self.max_len == other.max_len
+    }
+}
+
+impl Eq for Format {}
+
+#[derive(Copy, Clone, Debug, PartialEq, Eq)]
+struct DateField {
+    regex: &'static str,
+    unit: DateUnit,
+    max_len: usize,
+}
+
+impl DateField {
+    fn from_specifier(specifier: &str) -> Option<Self> {
+        match specifier {
+            "Y" => Some(DateField {
+                regex: r"\d{4}",
+                unit: DateUnit::Years,
+                max_len: 5,
+            }),
+            "y" => Some(DateField {
+                regex: r"\d\d",
+                unit: DateUnit::Years,
+                max_len: 2,
+            }),
+            "m" => Some(DateField {
+                regex: r"[0-1]\d",
+                unit: DateUnit::Months,
+                max_len: 2,
+            }),
+            "d" => Some(DateField {
+                regex: r"[0-3]\d",
+                unit: DateUnit::Days,
+                max_len: 2,
+            }),
+            "-d" => Some(DateField {
+                regex: r"[1-3]?\d",
+                unit: DateUnit::Days,
+                max_len: 2,
+            }),
+            "a" => Some(DateField {
+                regex: r"Sun|Mon|Tue|Wed|Thu|Fri|Sat",
+                unit: DateUnit::Days,
+                max_len: 3,
+            }),
+            "A" => Some(DateField {
+                regex: r"Sunday|Monday|Tuesday|Wednesday|Thursday|Friday|Saturday",
+                unit: DateUnit::Days,
+                max_len: 9,
+            }),
+            "b" | "h" => Some(DateField {
+                regex: r"Jan|Feb|Mar|Apr|May|Jun|Jul|Aug|Sep|Oct|Nov|Dec",
+                unit: DateUnit::Months,
+                max_len: 3,
+            }),
+            "B" => Some(DateField {
+                regex: r"January|February|March|April|May|June|July|August|September|October|November|December",
+                unit: DateUnit::Months,
+                max_len: 9,
+            }),
+            "H" => Some(DateField {
+                regex: r"[0-2]\d",
+                unit: DateUnit::Hours,
+                max_len: 2,
+            }),
+            "M" => Some(DateField {
+                regex: r"[0-5]\d",
+                unit: DateUnit::Minutes,
+                max_len: 2,
+            }),
+            "S" => Some(DateField {
+                regex: r"[0-5]\d",
+                unit: DateUnit::Seconds,
+                max_len: 2,
+            }),
+            "I" => Some(DateField {
+                regex: r"[0-1]\d",
+                unit: DateUnit::Hours,
+                max_len: 2,
+            }),
+            "-I" => Some(DateField {
+                regex: r"1?\d",
+                unit: DateUnit::Hours,
+                max_len: 2,
+            }),
+            "P" => Some(DateField {
+                regex: r"am|pm",
+                unit: DateUnit::AmPm,
+                max_len: 2,
+            }),
+            "p" => Some(DateField {
+                regex: r"AM|PM",
+                unit: DateUnit::AmPm,
+                max_len: 2,
+            }),
+            _ => None,
+        }
+    }
+}
+
+#[derive(Copy, Clone, Debug, PartialEq, Eq)]
+enum DateUnit {
+    Years,
+    Months,
+    Days,
+    Hours,
+    Minutes,
+    Seconds,
+    AmPm,
+}
+
+impl DateUnit {
+    fn is_date(self) -> bool {
+        matches!(self, DateUnit::Years | DateUnit::Months | DateUnit::Days)
+    }
+
+    fn is_time(self) -> bool {
+        matches!(
+            self,
+            DateUnit::Hours | DateUnit::Minutes | DateUnit::Seconds
+        )
+    }
+}
+
+fn ndays_in_month(year: i32, month: u32) -> u32 {
+    // The first day of the next month...
+    let (y, m) = if month == 12 {
+        (year + 1, 1)
+    } else {
+        (year, month + 1)
+    };
+    let d = NaiveDate::from_ymd(y, m, 1);
+
+    // ...is preceded by the last day of the original month.
+    d.pred().day()
+}
+
+fn add_months(date_time: NaiveDateTime, amount: i64) -> Option<NaiveDateTime> {
+    let month = (date_time.month0() as i64).checked_add(amount)?;
+    let year = date_time.year() + i32::try_from(month / 12).ok()?;
+    let year = if month.is_negative() { year - 1 } else { year };
+
+    // Normalize month
+    let month = month % 12;
+    let month = if month.is_negative() {
+        month + 12
+    } else {
+        month
+    } as u32
+        + 1;
+
+    let day = cmp::min(date_time.day(), ndays_in_month(year, month));
+
+    Some(NaiveDate::from_ymd(year, month, day).and_time(date_time.time()))
+}
+
+fn add_years(date_time: NaiveDateTime, amount: i64) -> Option<NaiveDateTime> {
+    let year = i32::try_from((date_time.year() as i64).checked_add(amount)?).ok()?;
+    let ndays = ndays_in_month(year, date_time.month());
+
+    if date_time.day() > ndays {
+        let d = NaiveDate::from_ymd(year, date_time.month(), ndays);
+        Some(d.succ().and_time(date_time.time()))
+    } else {
+        date_time.with_year(year)
+    }
+}
+
+fn add_duration(date_time: NaiveDateTime, duration: Duration) -> Option<NaiveDateTime> {
+    date_time.checked_add_signed(duration)
+}
+
+fn toggle_am_pm(date_time: NaiveDateTime) -> Option<NaiveDateTime> {
+    if date_time.hour() < 12 {
+        add_duration(date_time, Duration::hours(12))
+    } else {
+        add_duration(date_time, Duration::hours(-12))
+    }
+}
+
+#[cfg(test)]
+mod test {
+    use super::*;
+    use crate::Rope;
+
+    #[test]
+    fn test_increment_date_times() {
+        let tests = [
+            // (original, cursor, amount, expected)
+            ("2020-02-28", 0, 1, "2021-02-28"),
+            ("2020-02-29", 0, 1, "2021-03-01"),
+            ("2020-01-31", 5, 1, "2020-02-29"),
+            ("2020-01-20", 5, 1, "2020-02-20"),
+            ("2021-01-01", 5, -1, "2020-12-01"),
+            ("2021-01-31", 5, -2, "2020-11-30"),
+            ("2020-02-28", 8, 1, "2020-02-29"),
+            ("2021-02-28", 8, 1, "2021-03-01"),
+            ("2021-02-28", 0, -1, "2020-02-28"),
+            ("2021-03-01", 0, -1, "2020-03-01"),
+            ("2020-02-29", 5, -1, "2020-01-29"),
+            ("2020-02-20", 5, -1, "2020-01-20"),
+            ("2020-02-29", 8, -1, "2020-02-28"),
+            ("2021-03-01", 8, -1, "2021-02-28"),
+            ("1980/12/21", 8, 100, "1981/03/31"),
+            ("1980/12/21", 8, -100, "1980/09/12"),
+            ("1980/12/21", 8, 1000, "1983/09/17"),
+            ("1980/12/21", 8, -1000, "1978/03/27"),
+            ("2021-11-24 07:12:23", 0, 1, "2022-11-24 07:12:23"),
+            ("2021-11-24 07:12:23", 5, 1, "2021-12-24 07:12:23"),
+            ("2021-11-24 07:12:23", 8, 1, "2021-11-25 07:12:23"),
+            ("2021-11-24 07:12:23", 11, 1, "2021-11-24 08:12:23"),
+            ("2021-11-24 07:12:23", 14, 1, "2021-11-24 07:13:23"),
+            ("2021-11-24 07:12:23", 17, 1, "2021-11-24 07:12:24"),
+            ("2021/11/24 07:12:23", 0, 1, "2022/11/24 07:12:23"),
+            ("2021/11/24 07:12:23", 5, 1, "2021/12/24 07:12:23"),
+            ("2021/11/24 07:12:23", 8, 1, "2021/11/25 07:12:23"),
+            ("2021/11/24 07:12:23", 11, 1, "2021/11/24 08:12:23"),
+            ("2021/11/24 07:12:23", 14, 1, "2021/11/24 07:13:23"),
+            ("2021/11/24 07:12:23", 17, 1, "2021/11/24 07:12:24"),
+            ("2021-11-24 07:12", 0, 1, "2022-11-24 07:12"),
+            ("2021-11-24 07:12", 5, 1, "2021-12-24 07:12"),
+            ("2021-11-24 07:12", 8, 1, "2021-11-25 07:12"),
+            ("2021-11-24 07:12", 11, 1, "2021-11-24 08:12"),
+            ("2021-11-24 07:12", 14, 1, "2021-11-24 07:13"),
+            ("2021/11/24 07:12", 0, 1, "2022/11/24 07:12"),
+            ("2021/11/24 07:12", 5, 1, "2021/12/24 07:12"),
+            ("2021/11/24 07:12", 8, 1, "2021/11/25 07:12"),
+            ("2021/11/24 07:12", 11, 1, "2021/11/24 08:12"),
+            ("2021/11/24 07:12", 14, 1, "2021/11/24 07:13"),
+            ("Wed Nov 24 2021", 0, 1, "Thu Nov 25 2021"),
+            ("Wed Nov 24 2021", 4, 1, "Fri Dec 24 2021"),
+            ("Wed Nov 24 2021", 8, 1, "Thu Nov 25 2021"),
+            ("Wed Nov 24 2021", 11, 1, "Thu Nov 24 2022"),
+            ("24-Nov-2021", 0, 1, "25-Nov-2021"),
+            ("24-Nov-2021", 3, 1, "24-Dec-2021"),
+            ("24-Nov-2021", 7, 1, "24-Nov-2022"),
+            ("2021 Nov 24", 0, 1, "2022 Nov 24"),
+            ("2021 Nov 24", 5, 1, "2021 Dec 24"),
+            ("2021 Nov 24", 9, 1, "2021 Nov 25"),
+            ("Nov 24, 2021", 0, 1, "Dec 24, 2021"),
+            ("Nov 24, 2021", 4, 1, "Nov 25, 2021"),
+            ("Nov 24, 2021", 8, 1, "Nov 24, 2022"),
+            ("7:21:53 am", 0, 1, "8:21:53 am"),
+            ("7:21:53 am", 3, 1, "7:22:53 am"),
+            ("7:21:53 am", 5, 1, "7:21:54 am"),
+            ("7:21:53 am", 8, 1, "7:21:53 pm"),
+            ("7:21:53 AM", 0, 1, "8:21:53 AM"),
+            ("7:21:53 AM", 3, 1, "7:22:53 AM"),
+            ("7:21:53 AM", 5, 1, "7:21:54 AM"),
+            ("7:21:53 AM", 8, 1, "7:21:53 PM"),
+            ("7:21 am", 0, 1, "8:21 am"),
+            ("7:21 am", 3, 1, "7:22 am"),
+            ("7:21 am", 5, 1, "7:21 pm"),
+            ("7:21 AM", 0, 1, "8:21 AM"),
+            ("7:21 AM", 3, 1, "7:22 AM"),
+            ("7:21 AM", 5, 1, "7:21 PM"),
+            ("23:24:23", 1, 1, "00:24:23"),
+            ("23:24:23", 3, 1, "23:25:23"),
+            ("23:24:23", 6, 1, "23:24:24"),
+            ("23:24", 1, 1, "00:24"),
+            ("23:24", 3, 1, "23:25"),
+        ];
+
+        for (original, cursor, amount, expected) in tests {
+            let rope = Rope::from_str(original);
+            let range = Range::new(cursor, cursor + 1);
+            assert_eq!(
+                DateTimeIncrementor::from_range(rope.slice(..), range)
+                    .unwrap()
+                    .increment(amount)
+                    .1,
+                expected.into()
+            );
+        }
+    }
+
+    #[test]
+    fn test_invalid_date_times() {
+        let tests = [
+            "0000-00-00",
+            "1980-2-21",
+            "1980-12-1",
+            "12345",
+            "2020-02-30",
+            "1999-12-32",
+            "19-12-32",
+            "1-2-3",
+            "0000/00/00",
+            "1980/2/21",
+            "1980/12/1",
+            "12345",
+            "2020/02/30",
+            "1999/12/32",
+            "19/12/32",
+            "1/2/3",
+            "123:456:789",
+            "11:61",
+            "2021-55-12 08:12:54",
+        ];
+
+        for invalid in tests {
+            let rope = Rope::from_str(invalid);
+            let range = Range::new(0, 1);
+
+            assert_eq!(DateTimeIncrementor::from_range(rope.slice(..), range), None)
+        }
+    }
+}
diff --git a/helix-core/src/increment/mod.rs b/helix-core/src/increment/mod.rs
new file mode 100644
index 00000000..f5945774
--- /dev/null
+++ b/helix-core/src/increment/mod.rs
@@ -0,0 +1,8 @@
+pub mod date_time;
+pub mod number;
+
+use crate::{Range, Tendril};
+
+pub trait Increment {
+    fn increment(&self, amount: i64) -> (Range, Tendril);
+}
diff --git a/helix-core/src/numbers.rs b/helix-core/src/increment/number.rs
index e9f3c898..a19b7e75 100644
--- a/helix-core/src/numbers.rs
+++ b/helix-core/src/increment/number.rs
@@ -2,6 +2,8 @@ use std::borrow::Cow;
 
 use ropey::RopeSlice;
 
+use super::Increment;
+
 use crate::{
     textobject::{textobject_word, TextObject},
     Range, Tendril,
@@ -9,9 +11,9 @@ use crate::{
 
 #[derive(Debug, PartialEq, Eq)]
 pub struct NumberIncrementor<'a> {
-    pub range: Range,
-    pub value: i64,
-    pub radix: u32,
+    value: i64,
+    radix: u32,
+    range: Range,
 
     text: RopeSlice<'a>,
 }
@@ -71,9 +73,10 @@ impl<'a> NumberIncrementor<'a> {
             text,
         })
     }
+}
 
-    /// Add `amount` to the number and return the formatted text.
-    pub fn incremented_text(&self, amount: i64) -> Tendril {
+impl<'a> Increment for NumberIncrementor<'a> {
+    fn increment(&self, amount: i64) -> (Range, Tendril) {
         let old_text: Cow<str> = self.text.slice(self.range.from()..self.range.to()).into();
         let old_length = old_text.len();
         let new_value = self.value.wrapping_add(amount);
@@ -144,7 +147,7 @@ impl<'a> NumberIncrementor<'a> {
             }
         }
 
-        new_text.into()
+        (self.range, new_text.into())
     }
 }
 
@@ -366,7 +369,8 @@ mod test {
             assert_eq!(
                 NumberIncrementor::from_range(rope.slice(..), range)
                     .unwrap()
-                    .incremented_text(amount),
+                    .increment(amount)
+                    .1,
                 expected.into()
             );
         }
@@ -392,7 +396,8 @@ mod test {
             assert_eq!(
                 NumberIncrementor::from_range(rope.slice(..), range)
                     .unwrap()
-                    .incremented_text(amount),
+                    .increment(amount)
+                    .1,
                 expected.into()
             );
         }
@@ -419,7 +424,8 @@ mod test {
             assert_eq!(
                 NumberIncrementor::from_range(rope.slice(..), range)
                     .unwrap()
-                    .incremented_text(amount),
+                    .increment(amount)
+                    .1,
                 expected.into()
             );
         }
@@ -464,7 +470,8 @@ mod test {
             assert_eq!(
                 NumberIncrementor::from_range(rope.slice(..), range)
                     .unwrap()
-                    .incremented_text(amount),
+                    .increment(amount)
+                    .1,
                 expected.into()
             );
         }
@@ -491,7 +498,8 @@ mod test {
             assert_eq!(
                 NumberIncrementor::from_range(rope.slice(..), range)
                     .unwrap()
-                    .incremented_text(amount),
+                    .increment(amount)
+                    .1,
                 expected.into()
             );
         }
diff --git a/helix-core/src/lib.rs b/helix-core/src/lib.rs
index de7e95c1..92a59f31 100644
--- a/helix-core/src/lib.rs
+++ b/helix-core/src/lib.rs
@@ -5,18 +5,19 @@ pub mod diagnostic;
 pub mod diff;
 pub mod graphemes;
 pub mod history;
+pub mod increment;
 pub mod indent;
 pub mod line_ending;
 pub mod macros;
 pub mod match_brackets;
 pub mod movement;
-pub mod numbers;
 pub mod object;
 pub mod path;
 mod position;
 pub mod register;
 pub mod search;
 pub mod selection;
+pub mod shellwords;
 mod state;
 pub mod surround;
 pub mod syntax;
@@ -158,7 +159,7 @@ mod merge_toml_tests {
         ";
 
         let base: Value = toml::from_slice(include_bytes!("../../languages.toml"))
-            .expect("Couldn't parse built-in langauges config");
+            .expect("Couldn't parse built-in languages config");
         let user: Value = toml::from_str(USER).unwrap();
 
         let merged = merge_toml_values(base, user);
diff --git a/helix-core/src/register.rs b/helix-core/src/register.rs
index c5444eb7..b9eb497d 100644
--- a/helix-core/src/register.rs
+++ b/helix-core/src/register.rs
@@ -15,7 +15,11 @@ impl Register {
     }
 
     pub fn new_with_values(name: char, values: Vec<String>) -> Self {
-        Self { name, values }
+        if name == '_' {
+            Self::new(name)
+        } else {
+            Self { name, values }
+        }
     }
 
     pub const fn name(&self) -> char {
@@ -27,11 +31,15 @@ impl Register {
     }
 
     pub fn write(&mut self, values: Vec<String>) {
-        self.values = values;
+        if self.name != '_' {
+            self.values = values;
+        }
     }
 
     pub fn push(&mut self, value: String) {
-        self.values.push(value);
+        if self.name != '_' {
+            self.values.push(value);
+        }
     }
 }
 
diff --git a/helix-core/src/selection.rs b/helix-core/src/selection.rs
index b4d1dffa..116a1c7c 100644
--- a/helix-core/src/selection.rs
+++ b/helix-core/src/selection.rs
@@ -308,10 +308,10 @@ impl Range {
 }
 
 impl From<(usize, usize)> for Range {
-    fn from(tuple: (usize, usize)) -> Self {
+    fn from((anchor, head): (usize, usize)) -> Self {
         Self {
-            anchor: tuple.0,
-            head: tuple.1,
+            anchor,
+            head,
             horiz: None,
         }
     }
diff --git a/helix-core/src/shellwords.rs b/helix-core/src/shellwords.rs
new file mode 100644
index 00000000..13f6f3e9
--- /dev/null
+++ b/helix-core/src/shellwords.rs
@@ -0,0 +1,164 @@
+use std::borrow::Cow;
+
+/// Get the vec of escaped / quoted / doublequoted filenames from the input str
+pub fn shellwords(input: &str) -> Vec<Cow<'_, str>> {
+    enum State {
+        Normal,
+        NormalEscaped,
+        Quoted,
+        QuoteEscaped,
+        Dquoted,
+        DquoteEscaped,
+    }
+
+    use State::*;
+
+    let mut state = Normal;
+    let mut args: Vec<Cow<str>> = Vec::new();
+    let mut escaped = String::with_capacity(input.len());
+
+    let mut start = 0;
+    let mut end = 0;
+
+    for (i, c) in input.char_indices() {
+        state = match state {
+            Normal => match c {
+                '\\' => {
+                    escaped.push_str(&input[start..i]);
+                    start = i + 1;
+                    NormalEscaped
+                }
+                '"' => {
+                    end = i;
+                    Dquoted
+                }
+                '\'' => {
+                    end = i;
+                    Quoted
+                }
+                c if c.is_ascii_whitespace() => {
+                    end = i;
+                    Normal
+                }
+                _ => Normal,
+            },
+            NormalEscaped => Normal,
+            Quoted => match c {
+                '\\' => {
+                    escaped.push_str(&input[start..i]);
+                    start = i + 1;
+                    QuoteEscaped
+                }
+                '\'' => {
+                    end = i;
+                    Normal
+                }
+                _ => Quoted,
+            },
+            QuoteEscaped => Quoted,
+            Dquoted => match c {
+                '\\' => {
+                    escaped.push_str(&input[start..i]);
+                    start = i + 1;
+                    DquoteEscaped
+                }
+                '"' => {
+                    end = i;
+                    Normal
+                }
+                _ => Dquoted,
+            },
+            DquoteEscaped => Dquoted,
+        };
+
+        if i >= input.len() - 1 && end == 0 {
+            end = i + 1;
+        }
+
+        if end > 0 {
+            let esc_trim = escaped.trim();
+            let inp = &input[start..end];
+
+            if !(esc_trim.is_empty() && inp.trim().is_empty()) {
+                if esc_trim.is_empty() {
+                    args.push(inp.into());
+                } else {
+                    args.push([escaped, inp.into()].concat().into());
+                    escaped = "".to_string();
+                }
+            }
+            start = i + 1;
+            end = 0;
+        }
+    }
+    args
+}
+
+#[cfg(test)]
+mod test {
+    use super::*;
+
+    #[test]
+    fn test_normal() {
+        let input = r#":o single_word twó wörds \three\ \"with\ escaping\\"#;
+        let result = shellwords(input);
+        let expected = vec![
+            Cow::from(":o"),
+            Cow::from("single_word"),
+            Cow::from("twó"),
+            Cow::from("wörds"),
+            Cow::from(r#"three "with escaping\"#),
+        ];
+        // TODO test is_owned and is_borrowed, once they get stabilized.
+        assert_eq!(expected, result);
+    }
+
+    #[test]
+    fn test_quoted() {
+        let quoted =
+            r#":o 'single_word' 'twó wörds' '' ' ''\three\' \"with\ escaping\\' 'quote incomplete"#;
+        let result = shellwords(quoted);
+        let expected = vec![
+            Cow::from(":o"),
+            Cow::from("single_word"),
+            Cow::from("twó wörds"),
+            Cow::from(r#"three' "with escaping\"#),
+            Cow::from("quote incomplete"),
+        ];
+        assert_eq!(expected, result);
+    }
+
+    #[test]
+    fn test_dquoted() {
+        let dquoted = r#":o "single_word" "twó wörds" "" "  ""\three\' \"with\ escaping\\" "dquote incomplete"#;
+        let result = shellwords(dquoted);
+        let expected = vec![
+            Cow::from(":o"),
+            Cow::from("single_word"),
+            Cow::from("twó wörds"),
+            Cow::from(r#"three' "with escaping\"#),
+            Cow::from("dquote incomplete"),
+        ];
+        assert_eq!(expected, result);
+    }
+
+    #[test]
+    fn test_mixed() {
+        let dquoted = r#":o single_word 'twó wörds' "\three\' \"with\ escaping\\""no space before"'and after' $#%^@ "%^&(%^" ')(*&^%''a\\\\\b' '"#;
+        let result = shellwords(dquoted);
+        let expected = vec![
+            Cow::from(":o"),
+            Cow::from("single_word"),
+            Cow::from("twó wörds"),
+            Cow::from("three' \"with escaping\\"),
+            Cow::from("no space before"),
+            Cow::from("and after"),
+            Cow::from("$#%^@"),
+            Cow::from("%^&(%^"),
+            Cow::from(")(*&^%"),
+            Cow::from(r#"a\\b"#),
+            //last ' just changes to quoted but since we dont have anything after it, it should be ignored
+        ];
+        assert_eq!(expected, result);
+    }
+}
diff --git a/helix-core/src/surround.rs b/helix-core/src/surround.rs
index 32161b70..b53b0a78 100644
--- a/helix-core/src/surround.rs
+++ b/helix-core/src/surround.rs
@@ -1,4 +1,4 @@
-use crate::{search, Selection};
+use crate::{search, Range, Selection};
 use ropey::RopeSlice;
 
 pub const PAIRS: &[(char, char)] = &[
@@ -35,33 +35,27 @@ pub fn get_pair(ch: char) -> (char, char) {
 pub fn find_nth_pairs_pos(
     text: RopeSlice,
     ch: char,
-    pos: usize,
+    range: Range,
     n: usize,
 ) -> Option<(usize, usize)> {
-    let (open, close) = get_pair(ch);
-
-    if text.len_chars() < 2 || pos >= text.len_chars() {
+    if text.len_chars() < 2 || range.to() >= text.len_chars() {
         return None;
     }
 
+    let (open, close) = get_pair(ch);
+    let pos = range.cursor(text);
+
     if open == close {
         if Some(open) == text.get_char(pos) {
-            // Special case: cursor is directly on a matching char.
-            match pos {
-                0 => Some((pos, search::find_nth_next(text, close, pos + 1, n)?)),
-                _ if (pos + 1) == text.len_chars() => {
-                    Some((search::find_nth_prev(text, open, pos, n)?, pos))
-                }
-                // We return no match because there's no way to know which
-                // side of the char we should be searching on.
-                _ => None,
-            }
-        } else {
-            Some((
-                search::find_nth_prev(text, open, pos, n)?,
-                search::find_nth_next(text, close, pos, n)?,
-            ))
+            // Cursor is directly on match char. We return no match
+            // because there's no way to know which side of the char
+            // we should be searching on.
+            return None;
         }
+        Some((
+            search::find_nth_prev(text, open, pos, n)?,
+            search::find_nth_next(text, close, pos, n)?,
+        ))
     } else {
         Some((
             find_nth_open_pair(text, open, close, pos, n)?,
@@ -160,8 +154,8 @@ pub fn get_surround_pos(
 ) -> Option<Vec<usize>> {
     let mut change_pos = Vec::new();
 
-    for range in selection {
-        let (open_pos, close_pos) = find_nth_pairs_pos(text, ch, range.head, skip)?;
+    for &range in selection {
+        let (open_pos, close_pos) = find_nth_pairs_pos(text, ch, range, skip)?;
         if change_pos.contains(&open_pos) || change_pos.contains(&close_pos) {
             return None;
         }
@@ -178,67 +172,91 @@ mod test {
     use ropey::Rope;
     use smallvec::SmallVec;
 
-    #[test]
-    fn test_find_nth_pairs_pos() {
-        let doc = Rope::from("some (text) here");
+    fn check_find_nth_pair_pos(
+        text: &str,
+        cases: Vec<(usize, char, usize, Option<(usize, usize)>)>,
+    ) {
+        let doc = Rope::from(text);
         let slice = doc.slice(..);
 
-        // cursor on [t]ext
-        assert_eq!(find_nth_pairs_pos(slice, '(', 6, 1), Some((5, 10)));
-        assert_eq!(find_nth_pairs_pos(slice, ')', 6, 1), Some((5, 10)));
-        // cursor on so[m]e
-        assert_eq!(find_nth_pairs_pos(slice, '(', 2, 1), None);
-        // cursor on bracket itself
-        assert_eq!(find_nth_pairs_pos(slice, '(', 5, 1), Some((5, 10)));
-        assert_eq!(find_nth_pairs_pos(slice, '(', 10, 1), Some((5, 10)));
+        for (cursor_pos, ch, n, expected_range) in cases {
+            let range = find_nth_pairs_pos(slice, ch, (cursor_pos, cursor_pos + 1).into(), n);
+            assert_eq!(
+                range, expected_range,
+                "Expected {:?}, got {:?}",
+                expected_range, range
+            );
+        }
     }
 
     #[test]
-    fn test_find_nth_pairs_pos_skip() {
-        let doc = Rope::from("(so (many (good) text) here)");
-        let slice = doc.slice(..);
+    fn test_find_nth_pairs_pos() {
+        check_find_nth_pair_pos(
+            "some (text) here",
+            vec![
+                // cursor on [t]ext
+                (6, '(', 1, Some((5, 10))),
+                (6, ')', 1, Some((5, 10))),
+                // cursor on so[m]e
+                (2, '(', 1, None),
+                // cursor on bracket itself
+                (5, '(', 1, Some((5, 10))),
+                (10, '(', 1, Some((5, 10))),
+            ],
+        );
+    }
 
-        // cursor on go[o]d
-        assert_eq!(find_nth_pairs_pos(slice, '(', 13, 1), Some((10, 15)));
-        assert_eq!(find_nth_pairs_pos(slice, '(', 13, 2), Some((4, 21)));
-        assert_eq!(find_nth_pairs_pos(slice, '(', 13, 3), Some((0, 27)));
+    #[test]
+    fn test_find_nth_pairs_pos_skip() {
+        check_find_nth_pair_pos(
+            "(so (many (good) text) here)",
+            vec![
+                // cursor on go[o]d
+                (13, '(', 1, Some((10, 15))),
+                (13, '(', 2, Some((4, 21))),
+                (13, '(', 3, Some((0, 27))),
+            ],
+        );
     }
 
     #[test]
     fn test_find_nth_pairs_pos_same() {
-        let doc = Rope::from("'so 'many 'good' text' here'");
-        let slice = doc.slice(..);
-
-        // cursor on go[o]d
-        assert_eq!(find_nth_pairs_pos(slice, '\'', 13, 1), Some((10, 15)));
-        assert_eq!(find_nth_pairs_pos(slice, '\'', 13, 2), Some((4, 21)));
-        assert_eq!(find_nth_pairs_pos(slice, '\'', 13, 3), Some((0, 27)));
-        // cursor on the quotes
-        assert_eq!(find_nth_pairs_pos(slice, '\'', 10, 1), None);
-        // this is the best we can do since opening and closing pairs are same
-        assert_eq!(find_nth_pairs_pos(slice, '\'', 0, 1), Some((0, 4)));
-        assert_eq!(find_nth_pairs_pos(slice, '\'', 27, 1), Some((21, 27)));
+        check_find_nth_pair_pos(
+            "'so 'many 'good' text' here'",
+            vec![
+                // cursor on go[o]d
+                (13, '\'', 1, Some((10, 15))),
+                (13, '\'', 2, Some((4, 21))),
+                (13, '\'', 3, Some((0, 27))),
+                // cursor on the quotes
+                (10, '\'', 1, None),
+            ],
+        )
     }
 
     #[test]
     fn test_find_nth_pairs_pos_step() {
-        let doc = Rope::from("((so)((many) good (text))(here))");
-        let slice = doc.slice(..);
-
-        // cursor on go[o]d
-        assert_eq!(find_nth_pairs_pos(slice, '(', 15, 1), Some((5, 24)));
-        assert_eq!(find_nth_pairs_pos(slice, '(', 15, 2), Some((0, 31)));
+        check_find_nth_pair_pos(
+            "((so)((many) good (text))(here))",
+            vec![
+                // cursor on go[o]d
+                (15, '(', 1, Some((5, 24))),
+                (15, '(', 2, Some((0, 31))),
+            ],
+        )
     }
 
     #[test]
     fn test_find_nth_pairs_pos_mixed() {
-        let doc = Rope::from("(so [many {good} text] here)");
-        let slice = doc.slice(..);
-
-        // cursor on go[o]d
-        assert_eq!(find_nth_pairs_pos(slice, '{', 13, 1), Some((10, 15)));
-        assert_eq!(find_nth_pairs_pos(slice, '[', 13, 1), Some((4, 21)));
-        assert_eq!(find_nth_pairs_pos(slice, '(', 13, 1), Some((0, 27)));
+        check_find_nth_pair_pos(
+            "(so [many {good} text] here)",
+            vec![
+                // cursor on go[o]d
+                (13, '{', 1, Some((10, 15))),
+                (13, '[', 1, Some((4, 21))),
+                (13, '(', 1, Some((0, 27))),
+            ],
+        )
     }
 
     #[test]
diff --git a/helix-core/src/syntax.rs b/helix-core/src/syntax.rs
index 142265a8..ef35fc75 100644
--- a/helix-core/src/syntax.rs
+++ b/helix-core/src/syntax.rs
@@ -50,7 +50,7 @@ pub struct Configuration {
 #[serde(rename_all = "kebab-case", deny_unknown_fields)]
 pub struct LanguageConfiguration {
     #[serde(rename = "name")]
-    pub language_id: String,
+    pub language_id: String, // c-sharp, rust
     pub scope: String,           // source.rust
     pub file_types: Vec<String>, // filename ends_with? <Gemfile, rb, etc>
     #[serde(default)]
@@ -310,8 +310,9 @@ impl Loader {
 
     pub fn language_config_for_shebang(&self, source: &Rope) -> Option<Arc<LanguageConfiguration>> {
         let line = Cow::from(source.line(0));
-        static SHEBANG_REGEX: Lazy<Regex> =
-            Lazy::new(|| Regex::new(r"^#!\s*(?:\S*[/\\](?:env\s+)?)?([^\s\.\d]+)").unwrap());
+        static SHEBANG_REGEX: Lazy<Regex> = Lazy::new(|| {
+            Regex::new(r"^#!\s*(?:\S*[/\\](?:env\s+(?:\-\S+\s+)*)?)?([^\s\.\d]+)").unwrap()
+        });
         let configuration_id = SHEBANG_REGEX
             .captures(&line)
             .and_then(|cap| self.language_config_ids_by_shebang.get(&cap[1]));
diff --git a/helix-core/src/textobject.rs b/helix-core/src/textobject.rs
index 24f063d4..21ceec04 100644
--- a/helix-core/src/textobject.rs
+++ b/helix-core/src/textobject.rs
@@ -114,7 +114,7 @@ pub fn textobject_surround(
     ch: char,
     count: usize,
 ) -> Range {
-    surround::find_nth_pairs_pos(slice, ch, range.head, count)
+    surround::find_nth_pairs_pos(slice, ch, range, count)
         .map(|(anchor, head)| match textobject {
             TextObject::Inside => Range::new(next_grapheme_boundary(slice, anchor), head),
             TextObject::Around => Range::new(anchor, next_grapheme_boundary(slice, head)),
@@ -170,7 +170,7 @@ mod test {
 
     #[test]
     fn test_textobject_word() {
-        // (text, [(cursor position, textobject, final range), ...])
+        // (text, [(char position, textobject, final range), ...])
         let tests = &[
             (
                 "cursor at beginning of doc",
@@ -269,7 +269,9 @@ mod test {
             let slice = doc.slice(..);
             for &case in scenario {
                 let (pos, objtype, expected_range) = case;
-                let result = textobject_word(slice, Range::point(pos), objtype, 1, false);
+                // cursor is a single width selection
+                let range = Range::new(pos, pos + 1);
+                let result = textobject_word(slice, range, objtype, 1, false);
                 assert_eq!(
                     result,
                     expected_range.into(),
@@ -283,7 +285,7 @@ mod test {
 
     #[test]
     fn test_textobject_surround() {
-        // (text, [(cursor position, textobject, final range, count), ...])
+        // (text, [(cursor position, textobject, final range, surround char, count), ...])
         let tests = &[
             (
                 "simple (single) surround pairs",
diff --git a/helix-core/src/transaction.rs b/helix-core/src/transaction.rs
index dfc18fbe..d8d389f3 100644
--- a/helix-core/src/transaction.rs
+++ b/helix-core/src/transaction.rs
@@ -22,7 +22,7 @@ pub enum Assoc {
 }
 
 // ChangeSpec = Change | ChangeSet | Vec<Change>
-#[derive(Debug, Clone, PartialEq, Eq)]
+#[derive(Debug, Default, Clone, PartialEq, Eq)]
 pub struct ChangeSet {
     pub(crate) changes: Vec<Operation>,
     /// The required document length. Will refuse to apply changes unless it matches.
@@ -30,16 +30,6 @@ pub struct ChangeSet {
     len_after: usize,
 }
 
-impl Default for ChangeSet {
-    fn default() -> Self {
-        Self {
-            changes: Vec::new(),
-            len: 0,
-            len_after: 0,
-        }
-    }
-}
-
 impl ChangeSet {
     pub fn with_capacity(capacity: usize) -> Self {
         Self {
@@ -330,7 +320,7 @@ impl ChangeSet {
     /// `true` when the set is empty.
     #[inline]
     pub fn is_empty(&self) -> bool {
-        self.changes.is_empty()
+        self.changes.is_empty() || self.changes == [Operation::Retain(self.len)]
     }
 
     /// Map a position through the changes.
@@ -419,7 +409,7 @@ impl ChangeSet {
 
 /// Transaction represents a single undoable unit of changes. Several changes can be grouped into
 /// a single transaction.
-#[derive(Debug, Default, Clone)]
+#[derive(Debug, Default, Clone, PartialEq, Eq)]
 pub struct Transaction {
     changes: ChangeSet,
     selection: Option<Selection>,