Unify the standard properties checks in diff.

Instead of copy+pasting them into each compare function, we now call a shared function from a handful of places.

src/parser/keyword.rs

@@ -24,6 +24,7 @@ use crate::error::CustomError;
 use crate::error::MyError;
 use crate::error::Res;
 use crate::parser::util::start_of_line;
+use crate::types::BabelCall;
 use crate::types::Keyword;
 
 const ORG_ELEMENT_AFFILIATED_KEYWORDS: [&'static str; 13] = [
@@ -103,8 +104,16 @@ pub(crate) fn affiliated_keyword<'b, 'g, 'r, 's>(
 pub(crate) fn babel_call_keyword<'b, 'g, 'r, 's>(
     _context: RefContext<'b, 'g, 'r, 's>,
     input: OrgSource<'s>,
-) -> Res<OrgSource<'s>, Keyword<'s>> {
-    filtered_keyword(babel_call_key)(input)
+) -> Res<OrgSource<'s>, BabelCall<'s>> {
+    let (remaining, kw) = filtered_keyword(babel_call_key)(input)?;
+    Ok((
+        remaining,
+        BabelCall {
+            source: kw.source,
+            key: kw.key,
+            value: kw.value,
+        },
+    ))
 }
 
 #[cfg_attr(feature = "tracing", tracing::instrument(ret, level = "debug"))]