Fix footnote definition performance.

We were re-parsing each footnote definition in the footnote definition exit matcher which causes their contents to get re-parsed. This compounds with long lists of footnote definitions.

src/parser/citation.rs

@@ -2,7 +2,6 @@ use nom::branch::alt;
 use nom::bytes::complete::tag;
 use nom::bytes::complete::tag_no_case;
 use nom::character::complete::anychar;
-
 use nom::combinator::opt;
 use nom::combinator::recognize;
 use nom::combinator::verify;

src/parser/entity.rs

@@ -2,7 +2,6 @@ use nom::branch::alt;
 use nom::bytes::complete::tag;
 use nom::bytes::complete::tag_no_case;
 use nom::character::complete::satisfy;
-
 use nom::combinator::eof;
 use nom::combinator::peek;
 use nom::combinator::recognize;

src/parser/footnote_definition.rs

@@ -80,21 +80,10 @@ fn footnote_definition_end<'r, 's>(
     context: Context<'r, 's>,
     input: OrgSource<'s>,
 ) -> Res<OrgSource<'s>, OrgSource<'s>> {
-    let allow_nesting_context =
-        context.with_additional_node(ContextElement::Context("allow nesting footnotes"));
-    let footnote_definition_matcher = parser_with_context!(footnote_definition)(
-        if immediate_in_section(context, "footnote definition") {
-            &allow_nesting_context
-        } else {
-            context
-        },
-    );
-    let maybe_consume_trailing_whitespace_matcher =
-        parser_with_context!(maybe_consume_trailing_whitespace)(context);
     let (remaining, source) = alt((
         recognize(tuple((
-            maybe_consume_trailing_whitespace_matcher,
-            footnote_definition_matcher,
+            parser_with_context!(maybe_consume_trailing_whitespace)(context),
+            detect_footnote_definition,
         ))),
         recognize(tuple((
             start_of_line,
@@ -107,6 +96,12 @@ fn footnote_definition_end<'r, 's>(
     Ok((remaining, source))
 }
 
+#[cfg_attr(feature = "tracing", tracing::instrument(ret, level = "debug"))]
+fn detect_footnote_definition<'s>(input: OrgSource<'s>) -> Res<OrgSource<'s>, ()> {
+    tuple((start_of_line, tag_no_case("[fn:"), label, tag("]")))(input)?;
+    Ok((input, ()))
+}
+
 #[cfg(test)]
 mod tests {
     use super::*;

src/parser/inline_babel_call.rs

@@ -4,7 +4,6 @@ use nom::bytes::complete::tag_no_case;
 use nom::character::complete::anychar;
 use nom::character::complete::line_ending;
 use nom::character::complete::one_of;
-
 use nom::combinator::opt;
 use nom::combinator::recognize;
 use nom::combinator::verify;

src/parser/inline_source_block.rs

@@ -4,7 +4,6 @@ use nom::bytes::complete::tag_no_case;
 use nom::character::complete::anychar;
 use nom::character::complete::line_ending;
 use nom::character::complete::one_of;
-
 use nom::combinator::opt;
 use nom::combinator::recognize;
 use nom::combinator::verify;

src/parser/regular_link.rs

@@ -3,7 +3,6 @@ use nom::bytes::complete::escaped;
 use nom::bytes::complete::tag;
 use nom::bytes::complete::take_till1;
 use nom::character::complete::one_of;
-
 use nom::combinator::verify;
 use nom::multi::many_till;
 

src/parser/subscript_and_superscript.rs

@@ -2,7 +2,6 @@ use nom::branch::alt;
 use nom::bytes::complete::tag;
 use nom::character::complete::anychar;
 use nom::character::complete::one_of;
-
 use nom::combinator::map;
 use nom::combinator::not;
 use nom::combinator::opt;

src/parser/target.rs

@@ -1,7 +1,6 @@
 use nom::bytes::complete::tag;
 use nom::character::complete::anychar;
 use nom::character::complete::one_of;
-
 use nom::combinator::peek;
 use nom::combinator::recognize;
 use nom::combinator::verify;