Update README.md

README.md

@@ -22,14 +22,18 @@ Available for use and distribution under the [MIT license](LICENSE).
 
 In short, quite a lot. Standard and extended control flow, word expansion, most frequently used builtin commands, pipelines, redirection, variables, etc. The plumbing for completion is present, along with support for common cases (e.g. file/dir completion, basic support for programmable completion such as used with git and other tools). 
 
-### --Known limitations-- a.k.a. Where you can help!
+### <strike>Known limitations</strike> Where you can help!
 
 There's a lot that *is* working, but there are non-trivial gaps in compatibility. Most notably:
 
 * **Commands run asynchronously as jobs, job management.**
   You can run `some-command &` but it's proof-of-concept quality at best. Standard job management via `fg`, `bg`, and `jobs` is not fully implemented. This would be a great area for enthusiastic contributors to dive in :).
-* **Honoring `set` options (e.g., `set -e`).**
+* **Honoring `set` and `shopt` options (e.g., `set -e`).**
   The `set` builtin is implemented, as is `set -x` and a few other options, but most of the behaviors aren't there. `set -e`, for example, will execute but its semantics aren't applied across execution.
+* **Curly brace expansion.**
+  Most forms of expansion are implemented; for some reason, we never got around to implementing an expansion that turns `{a,b}` into `a b`. There's even a test for this, but it's marked as a known failing test.
+* **Tokenizer and parser edge cases.**
+  For simplicity and ease of getting going, the tokenizer for `brush` was hand-implemented and the parsers were implemented using [`rust-peg`](https://github.com/kevinmehall/rust-peg). (Also a huge shout out to that project!) There are some edge cases that got tricky and may not be implemented with 100% fidelity (e.g., complex nested parenthetical expressions in arithmetic expressions, further nested inside command substitutions). All of our tests are passing in these areas, but coverage is limited. Augmenting test coverage would be a great starting point.
 
 Shell built-ins are a mixed bag. Some are completely and fully implemented (e.g. echo), while some only support their most commonly used options. Some aren't implemented at all.