Some minor clippy fixes.

src/bin/cargo/cli.rs

@@ -118,7 +118,7 @@ Run with 'cargo -Z [FLAG] [SUBCOMMAND]'"
 pub fn get_version_string(is_verbose: bool) -> String {
     let version = cargo::version();
     let mut version_string = version.to_string();
-    version_string.push_str("\n");
+    version_string.push('\n');
     if is_verbose {
         version_string.push_str(&format!(
             "release: {}.{}.{}\n",

src/cargo/core/compiler/context/mod.rs

@@ -126,7 +126,7 @@ impl<'a, 'cfg> Context<'a, 'cfg> {
         let mut queue = JobQueue::new(self.bcx);
         let mut plan = BuildPlan::new();
         let build_plan = self.bcx.build_config.build_plan;
-        self.lto = super::lto::generate(&self.bcx)?;
+        self.lto = super::lto::generate(self.bcx)?;
         self.prepare_units()?;
         self.prepare()?;
         custom_build::build_map(&mut self)?;

src/cargo/core/compiler/custom_build.rs

@@ -349,8 +349,8 @@ fn build_work(cx: &mut Context<'_, '_>, unit: &Unit) -> CargoResult<Job> {
         let output = cmd
             .exec_with_streaming(
                 &mut |stdout| {
-                    if stdout.starts_with(CARGO_WARNING) {
-                        warnings_in_case_of_panic.push(stdout[CARGO_WARNING.len()..].to_owned());
+                    if let Some(warning) = stdout.strip_prefix(CARGO_WARNING) {
+                        warnings_in_case_of_panic.push(warning.to_owned());
                     }
                     if extra_verbose {
                         state.stdout(format!("{}{}", prefix, stdout));

src/cargo/core/compiler/fingerprint.rs

@@ -1975,9 +1975,7 @@ pub fn parse_rustc_dep_info(rustc_dep_info: &Path) -> CargoResult<RustcDepInfo>
     let mut found_deps = false;
 
     for line in contents.lines() {
-        let env_dep_prefix = "# env-dep:";
-        if line.starts_with(env_dep_prefix) {
-            let rest = &line[env_dep_prefix.len()..];
+        if let Some(rest) = line.strip_prefix("# env-dep:") {
             let mut parts = rest.splitn(2, '=');
             let env_var = match parts.next() {
                 Some(s) => s,

src/cargo/core/resolver/errors.rs

@@ -302,7 +302,7 @@ pub(super) fn activation_error(
                     ));
                 }
 
-                msg.push_str("\n");
+                msg.push('\n');
             }
             msg.push_str("required by ");
             msg.push_str(&describe_path(

src/cargo/ops/common_for_install_and_uninstall.rs

@@ -230,7 +230,7 @@ impl InstallTracker {
                 if let Some(p) = p.as_ref() {
                     msg.push_str(&format!(" as part of `{}`\n", p));
                 } else {
-                    msg.push_str("\n");
+                    msg.push('\n');
                 }
             }
             msg.push_str("Add --force to overwrite");

src/cargo/ops/fix.rs

@@ -614,9 +614,8 @@ impl FixArgs {
                 continue;
             }
             if let Some(s) = path.to_str() {
-                let prefix = "--edition=";
-                if s.starts_with(prefix) {
-                    ret.enabled_edition = Some(s[prefix.len()..].to_string());
+                if let Some(edition) = s.strip_prefix("--edition=") {
+                    ret.enabled_edition = Some(edition.to_string());
                     continue;
                 }
                 if s.starts_with("--error-format=") || s.starts_with("--json=") {

src/cargo/ops/lockfile.rs

@@ -151,7 +151,7 @@ fn serialize_resolve(resolve: &Resolve, orig: Option<&str>) -> String {
         for entry in list {
             out.push_str("[[patch.unused]]\n");
             emit_package(entry.as_table().unwrap(), &mut out);
-            out.push_str("\n");
+            out.push('\n');
         }
     }
 
@@ -214,7 +214,7 @@ fn emit_package(dep: &toml::value::Table, out: &mut String) {
 
             out.push_str("]\n");
         }
-        out.push_str("\n");
+        out.push('\n');
     } else if dep.contains_key("replace") {
         out.push_str(&format!("replace = {}\n\n", &dep["replace"]));
     }

src/cargo/sources/git/utils.rs

@@ -755,7 +755,7 @@ where
                 msg.push_str(attempt);
             }
         }
-        msg.push_str("\n");
+        msg.push('\n');
         if !ssh_agent_attempts.is_empty() {
             let names = ssh_agent_attempts
                 .iter()
@@ -1154,11 +1154,7 @@ fn github_up_to_date(
 
     // Trim off the `.git` from the repository, if present, since that's
     // optional for GitHub and won't work when we try to use the API as well.
-    let repository = if repository.ends_with(".git") {
-        &repository[..repository.len() - 4]
-    } else {
-        repository
-    };
+    let repository = repository.strip_suffix(".git").unwrap_or(repository);
 
     let url = format!(
         "https://api.github.com/repos/{}/{}/commits/{}",

src/cargo/util/config/key.rs

@@ -66,7 +66,7 @@ impl ConfigKey {
 
     fn _push(&mut self, env: &str, config: &str) {
         self.parts.push((config.to_string(), self.env.len()));
-        self.env.push_str("_");
+        self.env.push('_');
         self.env.push_str(env);
     }
 

src/cargo/util/progress.rs

@@ -266,20 +266,20 @@ impl Format {
         // Draw the `===>`
         if hashes > 0 {
             for _ in 0..hashes - 1 {
-                string.push_str("=");
+                string.push('=');
             }
             if cur == max {
-                string.push_str("=");
+                string.push('=');
             } else {
-                string.push_str(">");
+                string.push('>');
             }
         }
 
         // Draw the empty space we have left to do
         for _ in 0..(display_width - hashes) {
-            string.push_str(" ");
+            string.push(' ');
         }
-        string.push_str("]");
+        string.push(']');
         string.push_str(&stats);
 
         Some(string)

src/cargo/util/toml/mod.rs

@@ -1690,7 +1690,7 @@ impl DetailedTomlDependency {
                     .map(GitReference::Branch)
                     .or_else(|| self.tag.clone().map(GitReference::Tag))
                     .or_else(|| self.rev.clone().map(GitReference::Rev))
-                    .unwrap_or_else(|| GitReference::DefaultBranch);
+                    .unwrap_or(GitReference::DefaultBranch);
                 let loc = git.into_url()?;
 
                 if let Some(fragment) = loc.fragment() {