Fix issue #55

- This fixes an issue where we attempt to create a slice of bytes from a
string, assuming that two bytes doesn't end up in the middle of a
Unicode code point. Instead of comparing against the slice of bytes the
code now uses the String::starts_with() method to compare against the
same &str.
- Also adds a dev profile to Cargo.toml, which enables debug symbols and
turns down optimization.

Cargo.toml

@@ -31,3 +31,9 @@ wild = "2"
 [dev-dependencies]
 assert_cmd = "1.0.1"
 predicates = "1.0.5"
+
+# xref: https://bitshifter.github.io/rr+rust/#11
+# The development profile, used for `cargo build`
+[profile.dev]
+opt-level = 0  # Controls the --opt-level the compiler builds with
+debug = true   # Controls whether the compiler passes `-g`

src/main.rs

@@ -54,7 +54,7 @@ impl Rename {
         // Expand ~ if applicable.
         let mut new = new.to_string();
         if let Ok(home) = env::var("HOME") {
-            if &new[..2] == "~/" {
+            if new.starts_with("~/") {
                 new = new.replacen("~", &home, 1);
             }
         }