minor: save config.stderr() when we use it a lot

this also cleans up lines that get unnecessarily changed in the diff

src/rustdoc_cmd.rs

@@ -141,18 +141,19 @@ impl RustdocCommand {
         if !output.status.success() {
             if self.silence {
                 config.log_error(|config| {
+                    let mut stderr = config.stderr();
                     let delimiter = "-----";
                     writeln!(
-                        config.stderr(),
+                        stderr,
                         "error: running cargo-doc on crate {crate_name} failed with output:"
                     )?;
                     writeln!(
-                        config.stderr(),
+                        stderr,
                         "{delimiter}\n{}\n{delimiter}\n",
                         String::from_utf8_lossy(&output.stderr)
                     )?;
                     writeln!(
-                        config.stderr(),
+                        stderr,
                         "error: failed to build rustdoc for crate {crate_name} v{version}"
                     )?;
                     Ok(())
@@ -169,16 +170,17 @@ impl RustdocCommand {
             config.log_error(|config| {
                 let features =
                     crate_source.feature_list_from_config(config, crate_data.feature_config);
+                let mut stderr = config.stderr();
                 writeln!(
-                    config.stderr(),
+                    stderr,
                     "note: this is usually due to a compilation error in the crate,"
                 )?;
                 writeln!(
-                    config.stderr(),
+                    stderr,
                     "      and is unlikely to be a bug in cargo-semver-checks"
                 )?;
                 writeln!(
-                    config.stderr(),
+                    stderr,
                     "note: the following command can be used to reproduce the compilation error:"
                 )?;
                 let selector = match crate_source {
@@ -199,7 +201,7 @@ impl RustdocCommand {
                     format!("--features {} ", features.into_iter().join(","))
                 };
                 writeln!(
-                    config.stderr(),
+                    stderr,
                     "      \
 cargo new --lib example &&
           cd example &&
@@ -244,21 +246,22 @@ cargo new --lib example &&
                 } else {
                     config.log_error(|config| {
                         let delimiter = "-----";
+                        let mut stderr = config.stderr();
                         writeln!(
-                            config.stderr(),
+                            stderr,
                             "error: running cargo-config on crate {crate_name} failed with output:"
                         )?;
                         writeln!(
-                            config.stderr(),
+                            stderr,
                             "{delimiter}\n{}\n{delimiter}\n",
                             String::from_utf8_lossy(&output.stderr)
                         )?;
 
-                        writeln!(config.stderr(), "error: unexpected cargo config output for crate {crate_name} v{version}\n")?;
-                        writeln!(config.stderr(), "note: this may be a bug in cargo, or a bug in cargo-semver-checks;")?;
-                        writeln!(config.stderr(), "      if unsure, feel free to open a GitHub issue on cargo-semver-checks")?;
-                        writeln!(config.stderr(), "note: running the following command on the crate should reproduce the error:")?;
-                        writeln!(config.stderr(),
+                        writeln!(stderr, "error: unexpected cargo config output for crate {crate_name} v{version}\n")?;
+                        writeln!(stderr, "note: this may be a bug in cargo, or a bug in cargo-semver-checks;")?;
+                        writeln!(stderr, "      if unsure, feel free to open a GitHub issue on cargo-semver-checks")?;
+                        writeln!(stderr, "note: running the following command on the crate should reproduce the error:")?;
+                        writeln!(stderr,
                             "      cargo config -Zunstable-options get --format=json-value build.target\n",
                         )?;
                         Ok(())