regex: tweak DFA settings

This increases the limits a bit for when the regex engine will build and
use a fully compiled DFA. They can faster in some circumstances. For
example, '(?-u)^\w{30,}$' gets a nice speed boost from state
acceleration.

We are also able to remove `regex` proper as a dependency. Wow.

Cargo.lock

@@ -200,7 +200,6 @@ dependencies = [
  "bstr",
  "grep-matcher",
  "log",
- "regex",
  "regex-automata 0.3.0",
  "regex-syntax",
 ]

crates/regex/Cargo.toml

@@ -18,6 +18,5 @@ aho-corasick = "1.0.2"
 bstr = "1.5.0"
 grep-matcher = { version = "0.1.6", path = "../matcher" }
 log = "0.4.19"
-regex = "1.8.3"
-regex-automata = { version = "0.3.0" }
+regex-automata = "0.3.0"
 regex-syntax = "0.7.2"

crates/regex/src/config.rs

@@ -233,6 +233,15 @@ impl ConfiguredHIR {
         let meta = Regex::config()
             .utf8_empty(false)
             .nfa_size_limit(Some(self.config.size_limit))
+            // We don't expose a knob for this because the one-pass DFA is
+            // usually not a perf bottleneck for ripgrep. But we give it some
+            // extra room than the default.
+            .onepass_size_limit(Some(10 * (1 << 20)))
+            // Same deal here. The default limit for full DFAs is VERY small,
+            // but with ripgrep we can afford to spend a bit more time on
+            // building them I think.
+            .dfa_size_limit(Some(10 * (1 << 20)))
+            .dfa_state_limit(Some(10_000))
             .hybrid_cache_capacity(self.config.dfa_size_limit);
         Regex::builder()
             .configure(meta)