fix(help): Always trim output

This ensures we don't end up with accidental leading or trailing
newlines due to help template variables not being used when a section is
empty.

This is prep for removing name/version from the default template and is
part of clap-rs#4132

CHANGELOG.md

@@ -49,6 +49,7 @@ and this project adheres to [Semantic Versioning](http://semver.org/).
 - *(help)* Subcommands are now listed before arguments.  To get the old behavior, see `Command::help_template`
 - *(help)* Help headings are now title cased, making any user-provided help headings inconsistent.  To get the old behavior, see `Command::help_template`, `Arg::help_heading`, and `Command::subcommand_help_heading`
 - *(help)* "Command" is used as the section heading for subcommands and `COMMAND` for the value name.  To get the old behavior, see  `Command::subcommand_help_heading` and `Arg::subcommand_value_name`
+- *(help)* Whitespace in help output is now trimmed to ensure consistency regardless of how well a template matches the users needs.
 - *(env)* Parse `--help` and `--version` like any `ArgAction::SetTrue` flag (#3776)
 - *(derive)* Changed the default for arguments from `parse` to `value_parser`., removing `parse` support
 - *(derive)* `subcommand_required(true).arg_required_else_help(true)` is set instead of `SubcommandRequiredElseHelp` (#3280)
@@ -99,6 +100,7 @@ Deprecated
 - *(help)* Use `[positional]` in list when relevant (#4144)
 - *(help)* Show all `[positional]` in usage
 - *(help)* Polish up subcommands by referring to them as commands
+- *(help)* Trim extra whitespace to avoid artifacts from different uses of templates
 - *(version)* Use `Command::display_name` rather than `Command::bin_name`
 - *(parser)* Assert on unknown args when using external subcommands (#3703)
 - *(parser)* Always fill in `""` argument for external subcommands (#3263)

src/output/help.rs

@@ -106,6 +106,9 @@ impl<'cmd, 'writer> Help<'cmd, 'writer> {
             self.write_templated_help(template);
         }
 
+        // Remove any extra lines caused by book keeping
+        self.writer.trim();
+        // Ensure there is still a trailing newline
         self.none("\n");
     }
 }

tests/builder/help.rs

@@ -1627,7 +1627,7 @@ Options:
 
 NETWORKING:
     -n, --no-proxy    Do not use system proxy settings
-        --port        
+        --port
 ";
 
     let cmd = Command::new("blorp")
@@ -2853,7 +2853,7 @@ fn no_wrap_help() {
     let cmd = Command::new("ctest")
         .term_width(0)
         .override_help(MULTI_SC_HELP);
-    utils::assert_output(cmd, "ctest --help", &format!("{}\n", MULTI_SC_HELP), false);
+    utils::assert_output(cmd, "ctest --help", MULTI_SC_HELP, false);
 }
 
 #[test]