Change the usage misnomer to "description" (#13598)

# Description
    
The meaning of the word usage is specific to describing how a command
function is *used* and not a synonym for general description. Usage can
be used to describe the SYNOPSIS or EXAMPLES sections of a man page
where the permitted argument combinations are shown or example *uses*
are given.
Let's not confuse people and call it what it is a description.

Our `help` command already creates its own *Usage* section based on the
available arguments and doesn't refer to the description with usage.

# User-Facing Changes

`help commands` and `scope commands` will now use `description` or
`extra_description`
`usage`-> `description`
`extra_usage` -> `extra_description`

Breaking change in the plugin protocol:

In the signature record communicated with the engine.
`usage`-> `description`
`extra_usage` -> `extra_description`

The same rename also takes place for the methods on
`SimplePluginCommand` and `PluginCommand`

# Tests + Formatting
- Updated plugin protocol specific changes
# After Submitting
- [ ] update plugin protocol doc

crates/nu-cli/src/commands/commandline/commandline_.rs

@@ -14,7 +14,7 @@ impl Command for Commandline {
             .category(Category::Core)
     }
 
-    fn usage(&self) -> &str {
+    fn description(&self) -> &str {
         "View the current command line input buffer."
     }
 

crates/nu-cli/src/commands/commandline/edit.rs

@@ -34,7 +34,7 @@ impl Command for SubCommand {
             .category(Category::Core)
     }
 
-    fn usage(&self) -> &str {
+    fn description(&self) -> &str {
         "Modify the current command line input buffer."
     }
 

crates/nu-cli/src/commands/commandline/get_cursor.rs

@@ -16,7 +16,7 @@ impl Command for SubCommand {
             .category(Category::Core)
     }
 
-    fn usage(&self) -> &str {
+    fn description(&self) -> &str {
         "Get the current cursor position."
     }
 

crates/nu-cli/src/commands/commandline/set_cursor.rs

@@ -22,7 +22,7 @@ impl Command for SubCommand {
             .category(Category::Core)
     }
 
-    fn usage(&self) -> &str {
+    fn description(&self) -> &str {
         "Set the current cursor position."
     }
 

crates/nu-cli/src/commands/history/history_.rs

@@ -13,7 +13,7 @@ impl Command for History {
         "history"
     }
 
-    fn usage(&self) -> &str {
+    fn description(&self) -> &str {
         "Get the command history."
     }
 

crates/nu-cli/src/commands/history/history_session.rs

@@ -8,7 +8,7 @@ impl Command for HistorySession {
         "history session"
     }
 
-    fn usage(&self) -> &str {
+    fn description(&self) -> &str {
         "Get the command history session."
     }
 

crates/nu-cli/src/commands/keybindings.rs

@@ -14,11 +14,11 @@ impl Command for Keybindings {
             .input_output_types(vec![(Type::Nothing, Type::String)])
     }
 
-    fn usage(&self) -> &str {
+    fn description(&self) -> &str {
         "Keybindings related commands."
     }
 
-    fn extra_usage(&self) -> &str {
+    fn extra_description(&self) -> &str {
         r#"You must use one of the following subcommands. Using this command as-is will only produce this help message.
 
 For more information on input and keybindings, check:

crates/nu-cli/src/commands/keybindings_default.rs

@@ -15,7 +15,7 @@ impl Command for KeybindingsDefault {
             .input_output_types(vec![(Type::Nothing, Type::table())])
     }
 
-    fn usage(&self) -> &str {
+    fn description(&self) -> &str {
         "List default keybindings."
     }
 

crates/nu-cli/src/commands/keybindings_list.rs

@@ -23,7 +23,7 @@ impl Command for KeybindingsList {
             .category(Category::Platform)
     }
 
-    fn usage(&self) -> &str {
+    fn description(&self) -> &str {
         "List available options that can be used to create keybindings."
     }
 

crates/nu-cli/src/commands/keybindings_listen.rs

@@ -12,11 +12,11 @@ impl Command for KeybindingsListen {
         "keybindings listen"
     }
 
-    fn usage(&self) -> &str {
+    fn description(&self) -> &str {
         "Get input from the user."
     }
 
-    fn extra_usage(&self) -> &str {
+    fn extra_description(&self) -> &str {
         "This is an internal debugging tool. For better output, try `input listen --types [key]`"
     }
 

crates/nu-cli/src/menus/help_completions.rs

@@ -30,12 +30,15 @@ impl NuHelpCompleter {
             .filter_map(|(_, decl_id)| {
                 let decl = self.engine_state.get_decl(decl_id);
                 (decl.name().to_folded_case().contains(&folded_line)
-                    || decl.usage().to_folded_case().contains(&folded_line)
+                    || decl.description().to_folded_case().contains(&folded_line)
                     || decl
                         .search_terms()
                         .into_iter()
                         .any(|term| term.to_folded_case().contains(&folded_line))
-                    || decl.extra_usage().to_folded_case().contains(&folded_line))
+                    || decl
+                        .extra_description()
+                        .to_folded_case()
+                        .contains(&folded_line))
                 .then_some(decl)
             })
             .collect::<Vec<_>>();
@@ -47,15 +50,15 @@ impl NuHelpCompleter {
             .map(|decl| {
                 let mut long_desc = String::new();
 
-                let usage = decl.usage();
+                let description = decl.description();
-                if !usage.is_empty() {
+                if !description.is_empty() {
-                    long_desc.push_str(usage);
+                    long_desc.push_str(description);
                     long_desc.push_str("\r\n\r\n");
                 }
 
-                let extra_usage = decl.extra_usage();
+                let extra_desc = decl.extra_description();
-                if !extra_usage.is_empty() {
+                if !extra_desc.is_empty() {
-                    long_desc.push_str(extra_usage);
+                    long_desc.push_str(extra_desc);
                     long_desc.push_str("\r\n\r\n");
                 }
 

crates/nu-cli/src/nu_highlight.rs

@@ -17,7 +17,7 @@ impl Command for NuHighlight {
             .input_output_types(vec![(Type::String, Type::String)])
     }
 
-    fn usage(&self) -> &str {
+    fn description(&self) -> &str {
         "Syntax highlight the input string."
     }
 

crates/nu-cli/src/print.rs

@@ -30,11 +30,11 @@ impl Command for Print {
             .category(Category::Strings)
     }
 
-    fn usage(&self) -> &str {
+    fn description(&self) -> &str {
         "Print the given values to stdout."
     }
 
-    fn extra_usage(&self) -> &str {
+    fn extra_description(&self) -> &str {
         r#"Unlike `echo`, this command does not return any value (`print | describe` will return "nothing").
 Since this command has no output, there is no point in piping it with other commands.
 

crates/nu-cmd-extra/src/extra/bits/and.rs

@@ -37,7 +37,7 @@ impl Command for BitsAnd {
             .category(Category::Bits)
     }
 
-    fn usage(&self) -> &str {
+    fn description(&self) -> &str {
         "Performs bitwise and for ints or binary values."
     }
 

crates/nu-cmd-extra/src/extra/bits/bits_.rs

@@ -14,11 +14,11 @@ impl Command for Bits {
             .input_output_types(vec![(Type::Nothing, Type::String)])
     }
 
-    fn usage(&self) -> &str {
+    fn description(&self) -> &str {
         "Various commands for working with bits."
     }
 
-    fn extra_usage(&self) -> &str {
+    fn extra_description(&self) -> &str {
         "You must use one of the following subcommands. Using this command as-is will only produce this help message."
     }
 

crates/nu-cmd-extra/src/extra/bits/into.rs

@@ -45,7 +45,7 @@ impl Command for BitsInto {
             .category(Category::Conversions)
     }
 
-    fn usage(&self) -> &str {
+    fn description(&self) -> &str {
         "Convert value to a binary primitive."
     }
 

crates/nu-cmd-extra/src/extra/bits/not.rs

@@ -51,7 +51,7 @@ impl Command for BitsNot {
             .category(Category::Bits)
     }
 
-    fn usage(&self) -> &str {
+    fn description(&self) -> &str {
         "Performs logical negation on each bit."
     }
 

crates/nu-cmd-extra/src/extra/bits/or.rs

@@ -38,7 +38,7 @@ impl Command for BitsOr {
             .category(Category::Bits)
     }
 
-    fn usage(&self) -> &str {
+    fn description(&self) -> &str {
         "Performs bitwise or for ints or binary values."
     }
 

crates/nu-cmd-extra/src/extra/bits/rotate_left.rs

@@ -53,7 +53,7 @@ impl Command for BitsRol {
             .category(Category::Bits)
     }
 
-    fn usage(&self) -> &str {
+    fn description(&self) -> &str {
         "Bitwise rotate left for ints or binary values."
     }
 

crates/nu-cmd-extra/src/extra/bits/rotate_right.rs

@@ -53,7 +53,7 @@ impl Command for BitsRor {
             .category(Category::Bits)
     }
 
-    fn usage(&self) -> &str {
+    fn description(&self) -> &str {
         "Bitwise rotate right for ints or binary values."
     }
 

crates/nu-cmd-extra/src/extra/bits/shift_left.rs

@@ -55,7 +55,7 @@ impl Command for BitsShl {
             .category(Category::Bits)
     }
 
-    fn usage(&self) -> &str {
+    fn description(&self) -> &str {
         "Bitwise shift left for ints or binary values."
     }
 

crates/nu-cmd-extra/src/extra/bits/shift_right.rs

@@ -52,7 +52,7 @@ impl Command for BitsShr {
             .category(Category::Bits)
     }
 
-    fn usage(&self) -> &str {
+    fn description(&self) -> &str {
         "Bitwise shift right for ints or binary values."
     }
 

crates/nu-cmd-extra/src/extra/bits/xor.rs

@@ -38,7 +38,7 @@ impl Command for BitsXor {
             .category(Category::Bits)
     }
 
-    fn usage(&self) -> &str {
+    fn description(&self) -> &str {
         "Performs bitwise xor for ints or binary values."
     }
 

crates/nu-cmd-extra/src/extra/conversions/fmt.rs

@@ -9,7 +9,7 @@ impl Command for Fmt {
         "fmt"
     }
 
-    fn usage(&self) -> &str {
+    fn description(&self) -> &str {
         "Format a number."
     }
 

crates/nu-cmd-extra/src/extra/filters/each_while.rs

@@ -9,7 +9,7 @@ impl Command for EachWhile {
         "each while"
     }
 
-    fn usage(&self) -> &str {
+    fn description(&self) -> &str {
         "Run a closure on each row of the input list until a null is found, then create a new list with the results."
     }
 

crates/nu-cmd-extra/src/extra/filters/roll/roll_.rs

@@ -18,11 +18,11 @@ impl Command for Roll {
             .input_output_types(vec![(Type::Nothing, Type::String)])
     }
 
-    fn usage(&self) -> &str {
+    fn description(&self) -> &str {
         "Rolling commands for tables."
     }
 
-    fn extra_usage(&self) -> &str {
+    fn extra_description(&self) -> &str {
         "You must use one of the following subcommands. Using this command as-is will only produce this help message."
     }
 

crates/nu-cmd-extra/src/extra/filters/roll/roll_down.rs

@@ -21,7 +21,7 @@ impl Command for RollDown {
             .category(Category::Filters)
     }
 
-    fn usage(&self) -> &str {
+    fn description(&self) -> &str {
         "Roll table rows down."
     }
 

crates/nu-cmd-extra/src/extra/filters/roll/roll_left.rs

@@ -33,7 +33,7 @@ impl Command for RollLeft {
             .category(Category::Filters)
     }
 
-    fn usage(&self) -> &str {
+    fn description(&self) -> &str {
         "Roll record or table columns left."
     }
 

crates/nu-cmd-extra/src/extra/filters/roll/roll_right.rs

@@ -33,7 +33,7 @@ impl Command for RollRight {
             .category(Category::Filters)
     }
 
-    fn usage(&self) -> &str {
+    fn description(&self) -> &str {
         "Roll table columns right."
     }
 

crates/nu-cmd-extra/src/extra/filters/roll/roll_up.rs

@@ -21,7 +21,7 @@ impl Command for RollUp {
             .category(Category::Filters)
     }
 
-    fn usage(&self) -> &str {
+    fn description(&self) -> &str {
         "Roll table rows up."
     }
 

crates/nu-cmd-extra/src/extra/filters/rotate.rs

@@ -23,7 +23,7 @@ impl Command for Rotate {
             .category(Category::Filters)
     }
 
-    fn usage(&self) -> &str {
+    fn description(&self) -> &str {
         "Rotates a table or record clockwise (default) or counter-clockwise (use --ccw flag)."
     }
 

crates/nu-cmd-extra/src/extra/filters/update_cells.rs

@@ -27,7 +27,7 @@ impl Command for UpdateCells {
             .category(Category::Filters)
     }
 
-    fn usage(&self) -> &str {
+    fn description(&self) -> &str {
         "Update the table cells."
     }
 

crates/nu-cmd-extra/src/extra/formats/from/url.rs

@@ -14,7 +14,7 @@ impl Command for FromUrl {
             .category(Category::Formats)
     }
 
-    fn usage(&self) -> &str {
+    fn description(&self) -> &str {
         "Parse url-encoded string as a record."
     }
 

crates/nu-cmd-extra/src/extra/formats/to/html.rs

@@ -138,11 +138,11 @@ impl Command for ToHtml {
         ]
     }
 
-    fn usage(&self) -> &str {
+    fn description(&self) -> &str {
         "Convert table into simple HTML."
     }
 
-    fn extra_usage(&self) -> &str {
+    fn extra_description(&self) -> &str {
         "Screenshots of the themes can be browsed here: https://github.com/mbadolato/iTerm2-Color-Schemes."
     }
 

crates/nu-cmd-extra/src/extra/math/arccos.rs

@@ -22,7 +22,7 @@ impl Command for SubCommand {
             .category(Category::Math)
     }
 
-    fn usage(&self) -> &str {
+    fn description(&self) -> &str {
         "Returns the arccosine of the number."
     }
 

crates/nu-cmd-extra/src/extra/math/arccosh.rs

@@ -21,7 +21,7 @@ impl Command for SubCommand {
             .category(Category::Math)
     }
 
-    fn usage(&self) -> &str {
+    fn description(&self) -> &str {
         "Returns the inverse of the hyperbolic cosine function."
     }
 

crates/nu-cmd-extra/src/extra/math/arcsin.rs

@@ -22,7 +22,7 @@ impl Command for SubCommand {
             .category(Category::Math)
     }
 
-    fn usage(&self) -> &str {
+    fn description(&self) -> &str {
         "Returns the arcsine of the number."
     }
 

crates/nu-cmd-extra/src/extra/math/arcsinh.rs

@@ -21,7 +21,7 @@ impl Command for SubCommand {
             .category(Category::Math)
     }
 
-    fn usage(&self) -> &str {
+    fn description(&self) -> &str {
         "Returns the inverse of the hyperbolic sine function."
     }
 

crates/nu-cmd-extra/src/extra/math/arctan.rs

@@ -22,7 +22,7 @@ impl Command for SubCommand {
             .category(Category::Math)
     }
 
-    fn usage(&self) -> &str {
+    fn description(&self) -> &str {
         "Returns the arctangent of the number."
     }
 

crates/nu-cmd-extra/src/extra/math/arctanh.rs

@@ -21,7 +21,7 @@ impl Command for SubCommand {
             .category(Category::Math)
     }
 
-    fn usage(&self) -> &str {
+    fn description(&self) -> &str {
         "Returns the inverse of the hyperbolic tangent function."
     }
 

crates/nu-cmd-extra/src/extra/math/cos.rs

@@ -21,7 +21,7 @@ impl Command for SubCommand {
             .category(Category::Math)
     }
 
-    fn usage(&self) -> &str {
+    fn description(&self) -> &str {
         "Returns the cosine of the number."
     }
 

crates/nu-cmd-extra/src/extra/math/cosh.rs

@@ -21,7 +21,7 @@ impl Command for SubCommand {
             .category(Category::Math)
     }
 
-    fn usage(&self) -> &str {
+    fn description(&self) -> &str {
         "Returns the hyperbolic cosine of the number."
     }
 

crates/nu-cmd-extra/src/extra/math/exp.rs

@@ -21,7 +21,7 @@ impl Command for SubCommand {
             .category(Category::Math)
     }
 
-    fn usage(&self) -> &str {
+    fn description(&self) -> &str {
         "Returns e raised to the power of x."
     }
 

crates/nu-cmd-extra/src/extra/math/ln.rs

@@ -21,7 +21,7 @@ impl Command for SubCommand {
             .category(Category::Math)
     }
 
-    fn usage(&self) -> &str {
+    fn description(&self) -> &str {
         "Returns the natural logarithm. Base: (math e)."
     }
 

crates/nu-cmd-extra/src/extra/math/sin.rs

@@ -21,7 +21,7 @@ impl Command for SubCommand {
             .category(Category::Math)
     }
 
-    fn usage(&self) -> &str {
+    fn description(&self) -> &str {
         "Returns the sine of the number."
     }
 

crates/nu-cmd-extra/src/extra/math/sinh.rs

@@ -21,7 +21,7 @@ impl Command for SubCommand {
             .category(Category::Math)
     }
 
-    fn usage(&self) -> &str {
+    fn description(&self) -> &str {
         "Returns the hyperbolic sine of the number."
     }
 

crates/nu-cmd-extra/src/extra/math/tan.rs

@@ -21,7 +21,7 @@ impl Command for SubCommand {
             .category(Category::Math)
     }
 
-    fn usage(&self) -> &str {
+    fn description(&self) -> &str {
         "Returns the tangent of the number."
     }
 

crates/nu-cmd-extra/src/extra/math/tanh.rs

@@ -21,7 +21,7 @@ impl Command for SubCommand {
             .category(Category::Math)
     }
 
-    fn usage(&self) -> &str {
+    fn description(&self) -> &str {
         "Returns the hyperbolic tangent of the number."
     }
 

crates/nu-cmd-extra/src/extra/platform/ansi/gradient.rs

@@ -53,7 +53,7 @@ impl Command for SubCommand {
             .category(Category::Platform)
     }
 
-    fn usage(&self) -> &str {
+    fn description(&self) -> &str {
         "Add a color gradient (using ANSI color codes) to the given string."
     }
 

crates/nu-cmd-extra/src/extra/strings/encode_decode/decode_hex.rs

@@ -29,7 +29,7 @@ impl Command for DecodeHex {
             .category(Category::Formats)
     }
 
-    fn usage(&self) -> &str {
+    fn description(&self) -> &str {
         "Hex decode a value."
     }
 

crates/nu-cmd-extra/src/extra/strings/encode_decode/encode_hex.rs

@@ -29,7 +29,7 @@ impl Command for EncodeHex {
             .category(Category::Formats)
     }
 
-    fn usage(&self) -> &str {
+    fn description(&self) -> &str {
         "Encode a binary value using hex."
     }
 

crates/nu-cmd-extra/src/extra/strings/format/command.rs

@@ -24,7 +24,7 @@ impl Command for FormatPattern {
             .category(Category::Strings)
     }
 
-    fn usage(&self) -> &str {
+    fn description(&self) -> &str {
         "Format columns into a string using a simple pattern."
     }
 

crates/nu-cmd-extra/src/extra/strings/str_/case/camel_case.rs

@@ -30,7 +30,7 @@ impl Command for SubCommand {
             .category(Category::Strings)
     }
 
-    fn usage(&self) -> &str {
+    fn description(&self) -> &str {
         "Convert a string to camelCase."
     }
 

crates/nu-cmd-extra/src/extra/strings/str_/case/kebab_case.rs

@@ -30,7 +30,7 @@ impl Command for SubCommand {
             .category(Category::Strings)
     }
 
-    fn usage(&self) -> &str {
+    fn description(&self) -> &str {
         "Convert a string to kebab-case."
     }
 

crates/nu-cmd-extra/src/extra/strings/str_/case/pascal_case.rs

@@ -30,7 +30,7 @@ impl Command for SubCommand {
             .category(Category::Strings)
     }
 
-    fn usage(&self) -> &str {
+    fn description(&self) -> &str {
         "Convert a string to PascalCase."
     }
 

crates/nu-cmd-extra/src/extra/strings/str_/case/screaming_snake_case.rs

@@ -30,7 +30,7 @@ impl Command for SubCommand {
             .category(Category::Strings)
     }
 
-    fn usage(&self) -> &str {
+    fn description(&self) -> &str {
         "Convert a string to SCREAMING_SNAKE_CASE."
     }
 

crates/nu-cmd-extra/src/extra/strings/str_/case/snake_case.rs

@@ -30,7 +30,7 @@ impl Command for SubCommand {
             .category(Category::Strings)
     }
 
-    fn usage(&self) -> &str {
+    fn description(&self) -> &str {
         "Convert a string to snake_case."
     }
 

crates/nu-cmd-extra/src/extra/strings/str_/case/str_.rs

@@ -14,11 +14,11 @@ impl Command for Str {
             .input_output_types(vec![(Type::Nothing, Type::String)])
     }
 
-    fn usage(&self) -> &str {
+    fn description(&self) -> &str {
         "Various commands for working with string data."
     }
 
-    fn extra_usage(&self) -> &str {
+    fn extra_description(&self) -> &str {
         "You must use one of the following subcommands. Using this command as-is will only produce this help message."
     }
 

crates/nu-cmd-extra/src/extra/strings/str_/case/title_case.rs

@@ -30,7 +30,7 @@ impl Command for SubCommand {
             .category(Category::Strings)
     }
 
-    fn usage(&self) -> &str {
+    fn description(&self) -> &str {
         "Convert a string to Title Case."
     }
 

crates/nu-cmd-lang/src/core_commands/alias.rs

@@ -9,7 +9,7 @@ impl Command for Alias {
         "alias"
     }
 
-    fn usage(&self) -> &str {
+    fn description(&self) -> &str {
         "Alias a command (with optional flags) to a new name."
     }
 
@@ -25,7 +25,7 @@ impl Command for Alias {
             .category(Category::Core)
     }
 
-    fn extra_usage(&self) -> &str {
+    fn extra_description(&self) -> &str {
         r#"This command is a parser keyword. For details, check:
   https://www.nushell.sh/book/thinking_in_nu.html"#
     }

crates/nu-cmd-lang/src/core_commands/break_.rs

@@ -9,7 +9,7 @@ impl Command for Break {
         "break"
     }
 
-    fn usage(&self) -> &str {
+    fn description(&self) -> &str {
         "Break a loop."
     }
 
@@ -19,7 +19,7 @@ impl Command for Break {
             .category(Category::Core)
     }
 
-    fn extra_usage(&self) -> &str {
+    fn extra_description(&self) -> &str {
         r#"This command is a parser keyword. For details, check:
   https://www.nushell.sh/book/thinking_in_nu.html
 

crates/nu-cmd-lang/src/core_commands/collect.rs

@@ -25,11 +25,11 @@ impl Command for Collect {
             .category(Category::Filters)
     }
 
-    fn usage(&self) -> &str {
+    fn description(&self) -> &str {
         "Collect a stream into a value."
     }
 
-    fn extra_usage(&self) -> &str {
+    fn extra_description(&self) -> &str {
         r#"If provided, run a closure with the collected value as input.
 
 The entire stream will be collected into one value in memory, so if the stream

crates/nu-cmd-lang/src/core_commands/const_.rs

@@ -9,7 +9,7 @@ impl Command for Const {
         "const"
     }
 
-    fn usage(&self) -> &str {
+    fn description(&self) -> &str {
         "Create a parse-time constant."
     }
 
@@ -26,7 +26,7 @@ impl Command for Const {
             .category(Category::Core)
     }
 
-    fn extra_usage(&self) -> &str {
+    fn extra_description(&self) -> &str {
         r#"This command is a parser keyword. For details, check:
   https://www.nushell.sh/book/thinking_in_nu.html"#
     }

crates/nu-cmd-lang/src/core_commands/continue_.rs

@@ -9,7 +9,7 @@ impl Command for Continue {
         "continue"
     }
 
-    fn usage(&self) -> &str {
+    fn description(&self) -> &str {
         "Continue a loop from the next iteration."
     }
 
@@ -19,7 +19,7 @@ impl Command for Continue {
             .category(Category::Core)
     }
 
-    fn extra_usage(&self) -> &str {
+    fn extra_description(&self) -> &str {
         r#"This command is a parser keyword. For details, check:
   https://www.nushell.sh/book/thinking_in_nu.html
 

crates/nu-cmd-lang/src/core_commands/def.rs

@@ -9,7 +9,7 @@ impl Command for Def {
         "def"
     }
 
-    fn usage(&self) -> &str {
+    fn description(&self) -> &str {
         "Define a custom command."
     }
 
@@ -24,7 +24,7 @@ impl Command for Def {
             .category(Category::Core)
     }
 
-    fn extra_usage(&self) -> &str {
+    fn extra_description(&self) -> &str {
         r#"This command is a parser keyword. For details, check:
   https://www.nushell.sh/book/thinking_in_nu.html"#
     }

crates/nu-cmd-lang/src/core_commands/describe.rs

@@ -9,7 +9,7 @@ impl Command for Describe {
         "describe"
     }
 
-    fn usage(&self) -> &str {
+    fn description(&self) -> &str {
         "Describe the type and structure of the value(s) piped in."
     }
 

crates/nu-cmd-lang/src/core_commands/do_.rs

@@ -17,7 +17,7 @@ impl Command for Do {
         "do"
     }
 
-    fn usage(&self) -> &str {
+    fn description(&self) -> &str {
         "Run a closure, providing it with the pipeline input."
     }
 

crates/nu-cmd-lang/src/core_commands/echo.rs

@@ -8,7 +8,7 @@ impl Command for Echo {
         "echo"
     }
 
-    fn usage(&self) -> &str {
+    fn description(&self) -> &str {
         "Returns its arguments, ignoring the piped-in value."
     }
 
@@ -19,7 +19,7 @@ impl Command for Echo {
             .category(Category::Core)
     }
 
-    fn extra_usage(&self) -> &str {
+    fn extra_description(&self) -> &str {
         r#"Unlike `print`, which prints unstructured text to stdout, `echo` is like an
 identity function and simply returns its arguments. When given no arguments,
 it returns an empty string. When given one argument, it returns it as a

crates/nu-cmd-lang/src/core_commands/error_make.rs

@@ -25,7 +25,7 @@ impl Command for ErrorMake {
             .category(Category::Core)
     }
 
-    fn usage(&self) -> &str {
+    fn description(&self) -> &str {
         "Create an error."
     }
 

crates/nu-cmd-lang/src/core_commands/export.rs

@@ -15,11 +15,11 @@ impl Command for ExportCommand {
             .category(Category::Core)
     }
 
-    fn usage(&self) -> &str {
+    fn description(&self) -> &str {
         "Export definitions or environment variables from a module."
     }
 
-    fn extra_usage(&self) -> &str {
+    fn extra_description(&self) -> &str {
         r#"This command is a parser keyword. For details, check:
   https://www.nushell.sh/book/thinking_in_nu.html"#
     }

crates/nu-cmd-lang/src/core_commands/export_alias.rs

@@ -9,7 +9,7 @@ impl Command for ExportAlias {
         "export alias"
     }
 
-    fn usage(&self) -> &str {
+    fn description(&self) -> &str {
         "Alias a command (with optional flags) to a new name and export it from a module."
     }
 
@@ -25,7 +25,7 @@ impl Command for ExportAlias {
             .category(Category::Core)
     }
 
-    fn extra_usage(&self) -> &str {
+    fn extra_description(&self) -> &str {
         r#"This command is a parser keyword. For details, check:
   https://www.nushell.sh/book/thinking_in_nu.html"#
     }

crates/nu-cmd-lang/src/core_commands/export_const.rs

@@ -9,7 +9,7 @@ impl Command for ExportConst {
         "export const"
     }
 
-    fn usage(&self) -> &str {
+    fn description(&self) -> &str {
         "Use parse-time constant from a module and export them from this module."
     }
 
@@ -26,7 +26,7 @@ impl Command for ExportConst {
             .category(Category::Core)
     }
 
-    fn extra_usage(&self) -> &str {
+    fn extra_description(&self) -> &str {
         r#"This command is a parser keyword. For details, check:
   https://www.nushell.sh/book/thinking_in_nu.html"#
     }

crates/nu-cmd-lang/src/core_commands/export_def.rs

@@ -9,7 +9,7 @@ impl Command for ExportDef {
         "export def"
     }
 
-    fn usage(&self) -> &str {
+    fn description(&self) -> &str {
         "Define a custom command and export it from a module."
     }
 
@@ -24,7 +24,7 @@ impl Command for ExportDef {
             .category(Category::Core)
     }
 
-    fn extra_usage(&self) -> &str {
+    fn extra_description(&self) -> &str {
         r#"This command is a parser keyword. For details, check:
   https://www.nushell.sh/book/thinking_in_nu.html"#
     }

crates/nu-cmd-lang/src/core_commands/export_extern.rs

@@ -9,7 +9,7 @@ impl Command for ExportExtern {
         "export extern"
     }
 
-    fn usage(&self) -> &str {
+    fn description(&self) -> &str {
         "Define an extern and export it from a module."
     }
 
@@ -21,7 +21,7 @@ impl Command for ExportExtern {
             .category(Category::Core)
     }
 
-    fn extra_usage(&self) -> &str {
+    fn extra_description(&self) -> &str {
         r#"This command is a parser keyword. For details, check:
   https://www.nushell.sh/book/thinking_in_nu.html"#
     }

crates/nu-cmd-lang/src/core_commands/export_module.rs

@@ -9,7 +9,7 @@ impl Command for ExportModule {
         "export module"
     }
 
-    fn usage(&self) -> &str {
+    fn description(&self) -> &str {
         "Export a custom module from a module."
     }
 
@@ -26,7 +26,7 @@ impl Command for ExportModule {
             .category(Category::Core)
     }
 
-    fn extra_usage(&self) -> &str {
+    fn extra_description(&self) -> &str {
         r#"This command is a parser keyword. For details, check:
   https://www.nushell.sh/book/thinking_in_nu.html"#
     }

crates/nu-cmd-lang/src/core_commands/export_use.rs

@@ -9,7 +9,7 @@ impl Command for ExportUse {
         "export use"
     }
 
-    fn usage(&self) -> &str {
+    fn description(&self) -> &str {
         "Use definitions from a module and export them from this module."
     }
 
@@ -25,7 +25,7 @@ impl Command for ExportUse {
             .category(Category::Core)
     }
 
-    fn extra_usage(&self) -> &str {
+    fn extra_description(&self) -> &str {
         r#"This command is a parser keyword. For details, check:
   https://www.nushell.sh/book/thinking_in_nu.html"#
     }

crates/nu-cmd-lang/src/core_commands/extern_.rs

@@ -9,7 +9,7 @@ impl Command for Extern {
         "extern"
     }
 
-    fn usage(&self) -> &str {
+    fn description(&self) -> &str {
         "Define a signature for an external command."
     }
 
@@ -21,7 +21,7 @@ impl Command for Extern {
             .category(Category::Core)
     }
 
-    fn extra_usage(&self) -> &str {
+    fn extra_description(&self) -> &str {
         r#"This command is a parser keyword. For details, check:
   https://www.nushell.sh/book/thinking_in_nu.html"#
     }

crates/nu-cmd-lang/src/core_commands/for_.rs

@@ -9,7 +9,7 @@ impl Command for For {
         "for"
     }
 
-    fn usage(&self) -> &str {
+    fn description(&self) -> &str {
         "Loop over a range."
     }
 
@@ -32,7 +32,7 @@ impl Command for For {
             .category(Category::Core)
     }
 
-    fn extra_usage(&self) -> &str {
+    fn extra_description(&self) -> &str {
         r#"This command is a parser keyword. For details, check:
   https://www.nushell.sh/book/thinking_in_nu.html"#
     }

crates/nu-cmd-lang/src/core_commands/hide.rs

@@ -21,11 +21,11 @@ impl Command for Hide {
             .category(Category::Core)
     }
 
-    fn usage(&self) -> &str {
+    fn description(&self) -> &str {
         "Hide definitions in the current scope."
     }
 
-    fn extra_usage(&self) -> &str {
+    fn extra_description(&self) -> &str {
         r#"Definitions are hidden by priority: First aliases, then custom commands.
 
 This command is a parser keyword. For details, check:

crates/nu-cmd-lang/src/core_commands/hide_env.rs

@@ -25,7 +25,7 @@ impl Command for HideEnv {
             .category(Category::Core)
     }
 
-    fn usage(&self) -> &str {
+    fn description(&self) -> &str {
         "Hide environment variables in the current scope."
     }
 

crates/nu-cmd-lang/src/core_commands/if_.rs

@@ -14,7 +14,7 @@ impl Command for If {
         "if"
     }
 
-    fn usage(&self) -> &str {
+    fn description(&self) -> &str {
         "Conditionally run a block."
     }
 
@@ -41,7 +41,7 @@ impl Command for If {
             .category(Category::Core)
     }
 
-    fn extra_usage(&self) -> &str {
+    fn extra_description(&self) -> &str {
         r#"This command is a parser keyword. For details, check:
   https://www.nushell.sh/book/thinking_in_nu.html"#
     }

crates/nu-cmd-lang/src/core_commands/ignore.rs

@@ -9,7 +9,7 @@ impl Command for Ignore {
         "ignore"
     }
 
-    fn usage(&self) -> &str {
+    fn description(&self) -> &str {
         "Ignore the output of the previous command in the pipeline."
     }
 

crates/nu-cmd-lang/src/core_commands/let_.rs

@@ -9,7 +9,7 @@ impl Command for Let {
         "let"
     }
 
-    fn usage(&self) -> &str {
+    fn description(&self) -> &str {
         "Create a variable and give it a value."
     }
 
@@ -26,7 +26,7 @@ impl Command for Let {
             .category(Category::Core)
     }
 
-    fn extra_usage(&self) -> &str {
+    fn extra_description(&self) -> &str {
         r#"This command is a parser keyword. For details, check:
   https://www.nushell.sh/book/thinking_in_nu.html"#
     }

crates/nu-cmd-lang/src/core_commands/loop_.rs

@@ -9,7 +9,7 @@ impl Command for Loop {
         "loop"
     }
 
-    fn usage(&self) -> &str {
+    fn description(&self) -> &str {
         "Run a block in a loop."
     }
 
@@ -21,7 +21,7 @@ impl Command for Loop {
             .category(Category::Core)
     }
 
-    fn extra_usage(&self) -> &str {
+    fn extra_description(&self) -> &str {
         r#"This command is a parser keyword. For details, check:
   https://www.nushell.sh/book/thinking_in_nu.html"#
     }

crates/nu-cmd-lang/src/core_commands/match_.rs

@@ -11,7 +11,7 @@ impl Command for Match {
         "match"
     }
 
-    fn usage(&self) -> &str {
+    fn description(&self) -> &str {
         "Conditionally run a block on a matched value."
     }
 
@@ -27,7 +27,7 @@ impl Command for Match {
             .category(Category::Core)
     }
 
-    fn extra_usage(&self) -> &str {
+    fn extra_description(&self) -> &str {
         r#"This command is a parser keyword. For details, check:
   https://www.nushell.sh/book/thinking_in_nu.html"#
     }

crates/nu-cmd-lang/src/core_commands/module.rs

@@ -9,7 +9,7 @@ impl Command for Module {
         "module"
     }
 
-    fn usage(&self) -> &str {
+    fn description(&self) -> &str {
         "Define a custom module."
     }
 
@@ -26,7 +26,7 @@ impl Command for Module {
             .category(Category::Core)
     }
 
-    fn extra_usage(&self) -> &str {
+    fn extra_description(&self) -> &str {
         r#"This command is a parser keyword. For details, check:
   https://www.nushell.sh/book/thinking_in_nu.html"#
     }

crates/nu-cmd-lang/src/core_commands/mut_.rs

@@ -9,7 +9,7 @@ impl Command for Mut {
         "mut"
     }
 
-    fn usage(&self) -> &str {
+    fn description(&self) -> &str {
         "Create a mutable variable and give it a value."
     }
 
@@ -26,7 +26,7 @@ impl Command for Mut {
             .category(Category::Core)
     }
 
-    fn extra_usage(&self) -> &str {
+    fn extra_description(&self) -> &str {
         r#"This command is a parser keyword. For details, check:
   https://www.nushell.sh/book/thinking_in_nu.html"#
     }

crates/nu-cmd-lang/src/core_commands/overlay/command.rs

@@ -15,11 +15,11 @@ impl Command for Overlay {
             .input_output_types(vec![(Type::Nothing, Type::String)])
     }
 
-    fn usage(&self) -> &str {
+    fn description(&self) -> &str {
         "Commands for manipulating overlays."
     }
 
-    fn extra_usage(&self) -> &str {
+    fn extra_description(&self) -> &str {
         r#"This command is a parser keyword. For details, check:
   https://www.nushell.sh/book/thinking_in_nu.html
 

crates/nu-cmd-lang/src/core_commands/overlay/hide.rs

@@ -9,7 +9,7 @@ impl Command for OverlayHide {
         "overlay hide"
     }
 
-    fn usage(&self) -> &str {
+    fn description(&self) -> &str {
         "Hide an active overlay."
     }
 
@@ -31,7 +31,7 @@ impl Command for OverlayHide {
             .category(Category::Core)
     }
 
-    fn extra_usage(&self) -> &str {
+    fn extra_description(&self) -> &str {
         r#"This command is a parser keyword. For details, check:
   https://www.nushell.sh/book/thinking_in_nu.html"#
     }

crates/nu-cmd-lang/src/core_commands/overlay/list.rs

@@ -8,7 +8,7 @@ impl Command for OverlayList {
         "overlay list"
     }
 
-    fn usage(&self) -> &str {
+    fn description(&self) -> &str {
         "List all active overlays."
     }
 
@@ -18,7 +18,7 @@ impl Command for OverlayList {
             .input_output_types(vec![(Type::Nothing, Type::List(Box::new(Type::String)))])
     }
 
-    fn extra_usage(&self) -> &str {
+    fn extra_description(&self) -> &str {
         "The overlays are listed in the order they were activated."
     }
 

crates/nu-cmd-lang/src/core_commands/overlay/new.rs

@@ -9,7 +9,7 @@ impl Command for OverlayNew {
         "overlay new"
     }
 
-    fn usage(&self) -> &str {
+    fn description(&self) -> &str {
         "Create an empty overlay."
     }
 
@@ -27,7 +27,7 @@ impl Command for OverlayNew {
             .category(Category::Core)
     }
 
-    fn extra_usage(&self) -> &str {
+    fn extra_description(&self) -> &str {
         r#"The command will first create an empty module, then add it as an overlay.
 
 This command is a parser keyword. For details, check:

crates/nu-cmd-lang/src/core_commands/overlay/use_.rs

@@ -14,7 +14,7 @@ impl Command for OverlayUse {
         "overlay use"
     }
 
-    fn usage(&self) -> &str {
+    fn description(&self) -> &str {
         "Use definitions from a module as an overlay."
     }
 
@@ -45,7 +45,7 @@ impl Command for OverlayUse {
             .category(Category::Core)
     }
 
-    fn extra_usage(&self) -> &str {
+    fn extra_description(&self) -> &str {
         r#"This command is a parser keyword. For details, check:
   https://www.nushell.sh/book/thinking_in_nu.html"#
     }

crates/nu-cmd-lang/src/core_commands/return_.rs

@@ -9,7 +9,7 @@ impl Command for Return {
         "return"
     }
 
-    fn usage(&self) -> &str {
+    fn description(&self) -> &str {
         "Return early from a function."
     }
 
@@ -24,7 +24,7 @@ impl Command for Return {
             .category(Category::Core)
     }
 
-    fn extra_usage(&self) -> &str {
+    fn extra_description(&self) -> &str {
         r#"This command is a parser keyword. For details, check:
   https://www.nushell.sh/book/thinking_in_nu.html"#
     }

crates/nu-cmd-lang/src/core_commands/scope/aliases.rs

@@ -15,7 +15,7 @@ impl Command for ScopeAliases {
             .category(Category::Core)
     }
 
-    fn usage(&self) -> &str {
+    fn description(&self) -> &str {
         "Output info on the aliases in the current scope."
     }
 

crates/nu-cmd-lang/src/core_commands/scope/command.rs

@@ -15,7 +15,7 @@ impl Command for Scope {
             .allow_variants_without_examples(true)
     }
 
-    fn usage(&self) -> &str {
+    fn description(&self) -> &str {
         "Commands for getting info about what is in scope."
     }
 

crates/nu-cmd-lang/src/core_commands/scope/commands.rs

@@ -15,7 +15,7 @@ impl Command for ScopeCommands {
             .category(Category::Core)
     }
 
-    fn usage(&self) -> &str {
+    fn description(&self) -> &str {
         "Output info on the commands in the current scope."
     }
 

crates/nu-cmd-lang/src/core_commands/scope/engine_stats.rs

@@ -15,7 +15,7 @@ impl Command for ScopeEngineStats {
             .category(Category::Core)
     }
 
-    fn usage(&self) -> &str {
+    fn description(&self) -> &str {
         "Output stats on the engine in the current state."
     }
 

crates/nu-cmd-lang/src/core_commands/scope/externs.rs

@@ -15,7 +15,7 @@ impl Command for ScopeExterns {
             .category(Category::Core)
     }
 
-    fn usage(&self) -> &str {
+    fn description(&self) -> &str {
         "Output info on the known externals in the current scope."
     }
 

crates/nu-cmd-lang/src/core_commands/scope/modules.rs

@@ -15,7 +15,7 @@ impl Command for ScopeModules {
             .category(Category::Core)
     }
 
-    fn usage(&self) -> &str {
+    fn description(&self) -> &str {
         "Output info on the modules in the current scope."
     }
 

crates/nu-cmd-lang/src/core_commands/scope/variables.rs

@@ -15,7 +15,7 @@ impl Command for ScopeVariables {
             .category(Category::Core)
     }
 
-    fn usage(&self) -> &str {
+    fn description(&self) -> &str {
         "Output info on the variables in the current scope."
     }