Roll back dep updates

Unfortunately we can't have nice things because of the people who want
1.48.0 compatibility.

.circleci/config.yml

@@ -20,7 +20,7 @@ workflows:
               # get a nightly or stable toolchain via rustup instead of a mutable docker tag
               toolchain_override: [
                 '__msrv__', # won't add any other toolchains, just uses what's in the docker image
-                '1.70.0', # minimum needed to build dev-dependencies
+                '1.65.0', # minimum needed to build dev-dependencies
                 'stable',
                 'beta',
                 'nightly'

Cargo.toml

@@ -10,7 +10,7 @@ keywords = ["base64", "utf8", "encode", "decode", "no_std"]
 categories = ["encoding"]
 license = "MIT OR Apache-2.0"
 edition = "2018"
-# dev-dependencies require 1.70, but the main code doesn't
+# dev-dependencies require 1.65, but the main code doesn't
 # This option was added in 1.56, keep it for when we bump MSRV.
 rust-version = "1.48.0"
 
@@ -35,11 +35,11 @@ required-features = ["alloc"]
 rustdoc-args = ["--generate-link-to-definition"]
 
 [dev-dependencies]
-criterion = "0.5"
+criterion = "0.4.0"
 rand = { version = "0.8.5", features = ["small_rng"] }
-clap = { version = "4", features = ["derive"] }
+structopt = "0.3.26"
 # test fixtures for engine tests
-rstest = "0.18.0"
+rstest = "0.13.0"
 rstest_reuse = "0.6.0"
 once_cell = "1"
 

examples/base64.rs

@@ -5,15 +5,20 @@ use std::process;
 use std::str::FromStr;
 
 use base64::{alphabet, engine, read, write};
-use clap::{self, Parser};
+use structopt::StructOpt;
 
-#[derive(Copy, Clone, Debug, Default, Parser)]
+#[derive(Debug, StructOpt)]
 enum Alphabet {
-    #[default]
     Standard,
     UrlSafe,
 }
 
+impl Default for Alphabet {
+    fn default() -> Self {
+        Self::Standard
+    }
+}
+
 impl FromStr for Alphabet {
     type Err = String;
     fn from_str(s: &str) -> Result<Self, String> {
@@ -26,22 +31,22 @@ impl FromStr for Alphabet {
 }
 
 /// Base64 encode or decode FILE (or standard input), to standard output.
-#[derive(Debug, Parser)]
+#[derive(Debug, StructOpt)]
 struct Opt {
     /// decode data
-    #[arg(short, long)]
+    #[structopt(short = "d", long = "decode")]
     decode: bool,
     /// The alphabet to choose. Defaults to the standard base64 alphabet.
     /// Supported alphabets include "standard" and "urlsafe".
-    #[arg(short, long)]
+    #[structopt(long = "alphabet")]
     alphabet: Option<Alphabet>,
     /// The file to encode/decode.
-    #[arg(short, long)]
+    #[structopt(parse(from_os_str))]
     file: Option<PathBuf>,
 }
 
 fn main() {
-    let opt = Opt::parse();
+    let opt = Opt::from_args();
     let stdin;
     let mut input: Box<dyn Read> = match opt.file {
         None => {