Enforce required, optional, and rest positional arguments start with an uppercase and end with a period. (#11285)

# Description

This updates all the positional arguments (except with
`--features=dataframe` or `--features=extra`) to start with an uppercase
letter and end with a period.

Part of #5066, specifically [this
comment](/nushell/nushell/issues/5066#issuecomment-1421528910)

Some arguments had example data removed from them because it also
appears in the examples.

There are other inconsistencies in positional arguments I noticed while
making the tests pass which I will bring up in #5066.

# User-Facing Changes

Positional arguments are now consistent

# Tests + Formatting

- 🟢 `toolkit fmt`
- 🟢 `toolkit clippy`
- 🟢 `toolkit test`
- 🟢 `toolkit test stdlib`

# After Submitting

Automatic documentation updates

crates/nu-command/src/system/exec.rs

@@ -17,7 +17,7 @@ impl Command for Exec {
     fn signature(&self) -> Signature {
         Signature::build("exec")
             .input_output_types(vec![(Type::Nothing, Type::Any)])
-            .required("command", SyntaxShape::String, "the command to execute")
+            .required("command", SyntaxShape::String, "The command to execute.")
             .allows_unknown_args()
             .category(Category::System)
     }

crates/nu-command/src/system/nu_check.rs

@@ -20,7 +20,7 @@ impl Command for NuCheck {
             (Type::ListStream, Type::Bool),
             (Type::List(Box::new(Type::Any)), Type::Bool)])
             // type is string to avoid automatically canonicalizing the path
-            .optional("path", SyntaxShape::String, "File path to parse")
+            .optional("path", SyntaxShape::String, "File path to parse.")
             .switch("as-module", "Parse content as module", Some('m'))
             .switch("debug", "Show error messages", Some('d'))
             .switch("all", "Parse content as script first, returns result if success, otherwise, try with module", Some('a'))

crates/nu-command/src/system/registry_query.rs

@@ -38,11 +38,11 @@ impl Command for RegistryQuery {
                 "do not expand %ENV% placeholders in REG_EXPAND_SZ",
                 Some('u'),
             )
-            .required("key", SyntaxShape::String, "registry key to query")
+            .required("key", SyntaxShape::String, "Registry key to query.")
             .optional(
                 "value",
                 SyntaxShape::String,
-                "optionally supply a registry value to query",
+                "Optionally supply a registry value to query.",
             )
             .category(Category::System)
     }

crates/nu-command/src/system/run_external.rs

@@ -47,8 +47,8 @@ impl Command for External {
                 None,
             )
             .switch("trim-end-newline", "trimming end newlines", None)
-            .required("command", SyntaxShape::String, "external command to run")
-            .rest("args", SyntaxShape::Any, "arguments for external command")
+            .required("command", SyntaxShape::String, "External command to run.")
+            .rest("args", SyntaxShape::Any, "Arguments for external command.")
             .category(Category::System)
     }
 

crates/nu-command/src/system/which_.rs

@@ -24,8 +24,8 @@ impl Command for Which {
         Signature::build("which")
             .input_output_types(vec![(Type::Nothing, Type::Table(vec![]))])
             .allow_variants_without_examples(true)
-            .required("application", SyntaxShape::String, "application")
-            .rest("rest", SyntaxShape::String, "additional applications")
+            .required("application", SyntaxShape::String, "Application.")
+            .rest("rest", SyntaxShape::String, "Additional applications.")
             .switch("all", "list all executables", Some('a'))
             .category(Category::System)
     }