diff --git a/Cargo.toml b/Cargo.toml
index 1a3695c..97b80ca 100644
--- a/Cargo.toml
+++ b/Cargo.toml
@@ -26,7 +26,7 @@ time = { version = "0.3.11", features = ["formatting", "local-offset", "parsing"
 #! Optional Dependencies:
 
 ## Use `libgit2` as a backend for git operations
-git2 = { version = "0.18.0", default-features = false, optional = true }
+git2 = { version = "0.18.2", default-features = false, optional = true }
 
 ## Better support for querying the local system time
 tzdb = { version = "0.6.0", optional = true, default-features = false, features = ["local"] }
diff --git a/src/build.rs b/src/build.rs
index 12365d8..fed93a1 100644
--- a/src/build.rs
+++ b/src/build.rs
@@ -1,12 +1,8 @@
-use std::collections::BTreeMap;
+use std::fmt::{Display, Formatter};
 
 /// `shadow-rs` build constant identifiers.
 pub type ShadowConst = &'static str;
 
-pub trait ShadowGen {
-    fn gen_const(&self) -> BTreeMap<ShadowConst, ConstVal>;
-}
-
 /// Serialized values for build constants.
 #[derive(Debug, Clone)]
 pub struct ConstVal {
@@ -47,12 +43,12 @@ pub enum ConstType {
     Bool,
 }
 
-impl ToString for ConstType {
-    fn to_string(&self) -> String {
+impl Display for ConstType {
+    fn fmt(&self, f: &mut Formatter<'_>) -> std::fmt::Result {
         match self {
-            ConstType::OptStr => "Option<&str>".to_string(),
-            ConstType::Str => "&str".to_string(),
-            ConstType::Bool => "bool".to_string(),
+            ConstType::OptStr => write!(f, "Option<&str>"),
+            ConstType::Str => write!(f, "&str"),
+            ConstType::Bool => write!(f, "bool"),
         }
     }
 }
diff --git a/src/ci.rs b/src/ci.rs
index 518b864..c2c7b4c 100644
--- a/src/ci.rs
+++ b/src/ci.rs
@@ -1,3 +1,5 @@
+use std::fmt::{Display, Formatter};
+
 /// [`CiType`] holds the types of CI environment that `shadow-rs` can detect.
 #[derive(Debug)]
 pub enum CiType {
@@ -13,12 +15,12 @@ impl Default for CiType {
     }
 }
 
-impl ToString for CiType {
-    fn to_string(&self) -> String {
+impl Display for CiType {
+    fn fmt(&self, f: &mut Formatter<'_>) -> std::fmt::Result {
         match self {
-            CiType::Github => "github".into(),
-            CiType::Gitlab => "gitlab".into(),
-            _ => "none".into(),
+            CiType::Github => write!(f, "github"),
+            CiType::Gitlab => write!(f, "gitlab"),
+            _ => write!(f, "none"),
         }
     }
 }
diff --git a/src/err.rs b/src/err.rs
index f54ad2f..6cc0984 100644
--- a/src/err.rs
+++ b/src/err.rs
@@ -1,4 +1,3 @@
-use std::convert::From;
 use std::error::Error;
 use std::error::Error as StdError;
 use std::fmt::{Display, Formatter};
diff --git a/src/git.rs b/src/git.rs
index a024c30..deefb61 100644
--- a/src/git.rs
+++ b/src/git.rs
@@ -508,7 +508,6 @@ fn filter_git_dirty_stage(dirty_files: Vec<String>, staged_files: Vec<String>) -
 mod tests {
     use super::*;
     use crate::get_std_env;
-    use std::path::Path;
 
     #[test]
     fn test_git() {
@@ -535,7 +534,7 @@ mod tests {
 
     #[test]
     fn test_current_branch() {
-        if get_std_env().get("GITHUB_REF").is_some() {
+        if get_std_env().contains_key("GITHUB_REF") {
             return;
         }
         #[cfg(feature = "git2")]
diff --git a/src/lib.rs b/src/lib.rs
index 0e34418..c5360d6 100755
--- a/src/lib.rs
+++ b/src/lib.rs
@@ -446,7 +446,7 @@ impl Shadow {
                 #[allow(clippy::all)]\n\
             pub const {} :{} = r#\"{}\"#;",
                 shadow_const.to_ascii_uppercase(),
-                ConstType::Str.to_string(),
+                ConstType::Str,
                 ""
             ),
             ConstType::Str => format!(
@@ -454,14 +454,14 @@ impl Shadow {
                 #[allow(clippy::all)]\n\
             pub const {} :{} = r#\"{}\"#;",
                 shadow_const.to_ascii_uppercase(),
-                ConstType::Str.to_string(),
+                ConstType::Str,
                 val.v
             ),
             ConstType::Bool => format!(
                 "#[allow(dead_code)]\n\
             pub const {} :{} = {};",
                 shadow_const.to_ascii_uppercase(),
-                ConstType::Bool.to_string(),
+                ConstType::Bool,
                 val.v.parse::<bool>().unwrap()
             ),
         };