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-command/src/strings/char_.rs

@@ -193,7 +193,7 @@ impl Command for Char {
         true
     }
 
-    fn usage(&self) -> &str {
+    fn description(&self) -> &str {
         "Output special characters (e.g., 'newline')."
     }
 

crates/nu-command/src/strings/detect_columns.rs

@@ -37,7 +37,7 @@ impl Command for DetectColumns {
             .category(Category::Strings)
     }
 
-    fn usage(&self) -> &str {
+    fn description(&self) -> &str {
         "Attempt to automatically split text into multiple columns."
     }
 

crates/nu-command/src/strings/encode_decode/decode.rs

@@ -8,7 +8,7 @@ impl Command for Decode {
         "decode"
     }
 
-    fn usage(&self) -> &str {
+    fn description(&self) -> &str {
         "Decode bytes into a string."
     }
 
@@ -23,7 +23,7 @@ impl Command for Decode {
             .category(Category::Strings)
     }
 
-    fn extra_usage(&self) -> &str {
+    fn extra_description(&self) -> &str {
         r#"Multiple encodings are supported; here are a few:
 big5, euc-jp, euc-kr, gbk, iso-8859-1, utf-16, cp1252, latin5
 

crates/nu-command/src/strings/encode_decode/decode_base64.rs

@@ -40,11 +40,11 @@ impl Command for DecodeBase64 {
             .category(Category::Hash)
     }
 
-    fn usage(&self) -> &str {
+    fn description(&self) -> &str {
         "Base64 decode a value."
     }
 
-    fn extra_usage(&self) -> &str {
+    fn extra_description(&self) -> &str {
         r#"Will attempt to decode binary payload as an UTF-8 string by default. Use the `--binary(-b)` argument to force binary output."#
     }
 

crates/nu-command/src/strings/encode_decode/encode.rs

@@ -8,7 +8,7 @@ impl Command for Encode {
         "encode"
     }
 
-    fn usage(&self) -> &str {
+    fn description(&self) -> &str {
         // Note: "Encode a UTF-8 string into other forms" is semantically incorrect because
         // Nushell strings, as abstract values, have no user-facing encoding.
         // (Remember that "encoding" exclusively means "how the characters are
@@ -32,7 +32,7 @@ impl Command for Encode {
             .category(Category::Strings)
     }
 
-    fn extra_usage(&self) -> &str {
+    fn extra_description(&self) -> &str {
         r#"Multiple encodings are supported; here are a few:
 big5, euc-jp, euc-kr, gbk, iso-8859-1, cp1252, latin5
 

crates/nu-command/src/strings/encode_decode/encode_base64.rs

@@ -46,7 +46,7 @@ impl Command for EncodeBase64 {
             .category(Category::Hash)
     }
 
-    fn usage(&self) -> &str {
+    fn description(&self) -> &str {
         "Encode a string or binary value using Base64."
     }
 

crates/nu-command/src/strings/format/date.rs

@@ -30,7 +30,7 @@ impl Command for FormatDate {
             .category(Category::Strings)
     }
 
-    fn usage(&self) -> &str {
+    fn description(&self) -> &str {
         "Format a given date using a format string."
     }
 

crates/nu-command/src/strings/format/duration.rs

@@ -45,7 +45,7 @@ impl Command for FormatDuration {
             .category(Category::Strings)
     }
 
-    fn usage(&self) -> &str {
+    fn description(&self) -> &str {
         "Outputs duration with a specified unit of time."
     }
 

crates/nu-command/src/strings/format/filesize.rs

@@ -42,7 +42,7 @@ impl Command for FormatFilesize {
             .category(Category::Strings)
     }
 
-    fn usage(&self) -> &str {
+    fn description(&self) -> &str {
         "Converts a column of filesizes to some specified format."
     }
 

crates/nu-command/src/strings/format/format_.rs

@@ -14,11 +14,11 @@ impl Command for Format {
             .input_output_types(vec![(Type::Nothing, Type::String)])
     }
 
-    fn usage(&self) -> &str {
+    fn description(&self) -> &str {
         "Various commands for formatting 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-command/src/strings/parse.rs

@@ -11,7 +11,7 @@ impl Command for Parse {
         "parse"
     }
 
-    fn usage(&self) -> &str {
+    fn description(&self) -> &str {
         "Parse columns from string data using a simple pattern or a supplied regular expression."
     }
 
@@ -19,7 +19,7 @@ impl Command for Parse {
         vec!["pattern", "match", "regex", "str extract"]
     }
 
-    fn extra_usage(&self) -> &str {
+    fn extra_description(&self) -> &str {
         "The parse command always uses regular expressions even when you use a simple pattern. If a simple pattern is supplied, parse will transform that pattern into a regular expression."
     }
 

crates/nu-command/src/strings/split/chars.rs

@@ -30,7 +30,7 @@ impl Command for SubCommand {
             .category(Category::Strings)
     }
 
-    fn usage(&self) -> &str {
+    fn description(&self) -> &str {
         "Split a string into a list of characters."
     }
 

crates/nu-command/src/strings/split/column.rs

@@ -35,7 +35,7 @@ impl Command for SubCommand {
             .category(Category::Strings)
     }
 
-    fn usage(&self) -> &str {
+    fn description(&self) -> &str {
         "Split a string into multiple columns using a separator."
     }
 

crates/nu-command/src/strings/split/command.rs

@@ -14,11 +14,11 @@ impl Command for SplitCommand {
             .input_output_types(vec![(Type::Nothing, Type::String)])
     }
 
-    fn usage(&self) -> &str {
+    fn description(&self) -> &str {
         "Split contents across desired subcommand (like row, column) via the separator."
     }
 
-    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-command/src/strings/split/list.rs

@@ -28,7 +28,7 @@ impl Command for SubCommand {
             .category(Category::Filters)
     }
 
-    fn usage(&self) -> &str {
+    fn description(&self) -> &str {
         "Split a list into multiple lists using a separator."
     }
 

crates/nu-command/src/strings/split/row.rs

@@ -35,7 +35,7 @@ impl Command for SubCommand {
             .category(Category::Strings)
     }
 
-    fn usage(&self) -> &str {
+    fn description(&self) -> &str {
         "Split a string into multiple rows using a separator."
     }
 

crates/nu-command/src/strings/split/words.rs

@@ -56,7 +56,7 @@ impl Command for SubCommand {
             )
     }
 
-    fn usage(&self) -> &str {
+    fn description(&self) -> &str {
         "Split a string's words into separate rows."
     }
 

crates/nu-command/src/strings/str_/case/capitalize.rs

@@ -28,7 +28,7 @@ impl Command for SubCommand {
             .category(Category::Strings)
     }
 
-    fn usage(&self) -> &str {
+    fn description(&self) -> &str {
         "Capitalize first letter of text."
     }
 

crates/nu-command/src/strings/str_/case/downcase.rs

@@ -28,7 +28,7 @@ impl Command for SubCommand {
             .category(Category::Strings)
     }
 
-    fn usage(&self) -> &str {
+    fn description(&self) -> &str {
         "Make text lowercase."
     }
 

crates/nu-command/src/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-command/src/strings/str_/case/upcase.rs

@@ -28,7 +28,7 @@ impl Command for SubCommand {
             .category(Category::Strings)
     }
 
-    fn usage(&self) -> &str {
+    fn description(&self) -> &str {
         "Make text uppercase."
     }
 

crates/nu-command/src/strings/str_/contains.rs

@@ -42,7 +42,7 @@ impl Command for SubCommand {
             .category(Category::Strings)
     }
 
-    fn usage(&self) -> &str {
+    fn description(&self) -> &str {
         "Checks if string input contains a substring."
     }
 

crates/nu-command/src/strings/str_/deunicode.rs

@@ -17,7 +17,7 @@ impl Command for SubCommand {
             .category(Category::Strings)
     }
 
-    fn usage(&self) -> &str {
+    fn description(&self) -> &str {
         "Convert Unicode string to pure ASCII."
     }
 

crates/nu-command/src/strings/str_/distance.rs

@@ -41,7 +41,7 @@ impl Command for SubCommand {
             .category(Category::Strings)
     }
 
-    fn usage(&self) -> &str {
+    fn description(&self) -> &str {
         "Compare two strings and return the edit distance/Levenshtein distance."
     }
 

crates/nu-command/src/strings/str_/ends_with.rs

@@ -42,7 +42,7 @@ impl Command for SubCommand {
             .category(Category::Strings)
     }
 
-    fn usage(&self) -> &str {
+    fn description(&self) -> &str {
         "Check if an input ends with a string."
     }
 

crates/nu-command/src/strings/str_/expand.rs

@@ -8,11 +8,11 @@ impl Command for SubCommand {
         "str expand"
     }
 
-    fn usage(&self) -> &str {
+    fn description(&self) -> &str {
         "Generates all possible combinations defined in brace expansion syntax."
     }
 
-    fn extra_usage(&self) -> &str {
+    fn extra_description(&self) -> &str {
         "This syntax may seem familiar with `glob {A,B}.C`. The difference is glob relies on filesystem, but str expand is not. Inside braces, we put variants. Then basically we're creating all possible outcomes."
     }
 

crates/nu-command/src/strings/str_/index_of.rs

@@ -64,7 +64,7 @@ impl Command for SubCommand {
             .category(Category::Strings)
     }
 
-    fn usage(&self) -> &str {
+    fn description(&self) -> &str {
         "Returns start index of first occurrence of string in input, or -1 if no match."
     }
 

crates/nu-command/src/strings/str_/join.rs

@@ -26,7 +26,7 @@ impl Command for StrJoin {
             .category(Category::Strings)
     }
 
-    fn usage(&self) -> &str {
+    fn description(&self) -> &str {
         "Concatenate multiple strings into a single string, with an optional separator between each."
     }
 

crates/nu-command/src/strings/str_/length.rs

@@ -50,7 +50,7 @@ impl Command for SubCommand {
             .category(Category::Strings)
     }
 
-    fn usage(&self) -> &str {
+    fn description(&self) -> &str {
         "Output the length of any strings in the pipeline."
     }
 

crates/nu-command/src/strings/str_/replace.rs

@@ -65,7 +65,7 @@ impl Command for SubCommand {
             .category(Category::Strings)
     }
 
-    fn usage(&self) -> &str {
+    fn description(&self) -> &str {
         "Find and replace text."
     }
 

crates/nu-command/src/strings/str_/reverse.rs

@@ -29,7 +29,7 @@ impl Command for SubCommand {
             .category(Category::Strings)
     }
 
-    fn usage(&self) -> &str {
+    fn description(&self) -> &str {
         "Reverse every string in the pipeline."
     }
 

crates/nu-command/src/strings/str_/starts_with.rs

@@ -43,7 +43,7 @@ impl Command for SubCommand {
             .category(Category::Strings)
     }
 
-    fn usage(&self) -> &str {
+    fn description(&self) -> &str {
         "Check if an input starts with a string."
     }
 

crates/nu-command/src/strings/str_/stats.rs

@@ -22,7 +22,7 @@ impl Command for SubCommand {
             .input_output_types(vec![(Type::String, Type::record())])
     }
 
-    fn usage(&self) -> &str {
+    fn description(&self) -> &str {
         "Gather word count statistics on the text."
     }
 

crates/nu-command/src/strings/str_/substring.rs

@@ -68,7 +68,7 @@ impl Command for SubCommand {
             .category(Category::Strings)
     }
 
-    fn usage(&self) -> &str {
+    fn description(&self) -> &str {
         "Get part of a string. Note that the first character of a string is index 0."
     }
 

crates/nu-command/src/strings/str_/trim/trim_.rs

@@ -63,7 +63,7 @@ impl Command for SubCommand {
             )
             .category(Category::Strings)
     }
-    fn usage(&self) -> &str {
+    fn description(&self) -> &str {
         "Trim whitespace or specific character."
     }