Pull in fewer dependencies

Cargo.toml

@@ -27,5 +27,4 @@ syn = { version = "1.0", features = ["full"] }
 proc-macro2 = { version = "1.0", features = ["span-locations"] }
 toml = "0.5"
 url = "2.0"
-itertools = "0.9"
-regex = "1.1"
+regex = { version = "1.3", default-features = false, features = ["std", "unicode"] }

src/helpers.rs

@@ -1,14 +1,35 @@
+use std::fmt::Display;
 use std::fs::File;
 use std::io::{self, Read};
 use std::result;
 
-use itertools::join;
 use semver_parser::range::{Op, VersionReq};
 use semver_parser::version::Version;
 
 /// The common result type, our errors will be simple strings.
 pub type Result<T> = result::Result<T, String>;
 
+fn join<T>(iter: T, sep: &str) -> String
+where
+    T: IntoIterator,
+    T::Item: Display,
+{
+    let mut buf = String::new();
+    let mut iter = iter.into_iter();
+    if let Some(item) = iter.next() {
+        let item = item.to_string();
+        buf.push_str(&item);
+    } else {
+        return buf;
+    }
+    for item in iter {
+        buf.push_str(sep);
+        let item = item.to_string();
+        buf.push_str(&item);
+    }
+    buf
+}
+
 /// Return all data from `path`.
 pub fn read_file(path: &str) -> io::Result<String> {
     let mut file = File::open(path)?;