Add command_prelude module (#12291)

# Description
When implementing a `Command`, one must also import all the types
present in the function signatures for `Command`. This makes it so that
we often import the same set of types in each command implementation
file. E.g., something like this:
```rust
use nu_protocol::ast::Call;
use nu_protocol::engine::{Command, EngineState, Stack};
use nu_protocol::{
    record, Category, Example, IntoInterruptiblePipelineData, IntoPipelineData, PipelineData,
    ShellError, Signature, Span, Type, Value,
};
```

This PR adds the `nu_engine::command_prelude` module which contains the
necessary and commonly used types to implement a `Command`:
```rust
// command_prelude.rs
pub use crate::CallExt;
pub use nu_protocol::{
    ast::{Call, CellPath},
    engine::{Command, EngineState, Stack},
    record, Category, Example, IntoInterruptiblePipelineData, IntoPipelineData, IntoSpanned,
    PipelineData, Record, ShellError, Signature, Span, Spanned, SyntaxShape, Type, Value,
};
```

This should reduce the boilerplate needed to implement a command and
also gives us a place to track the breadth of the `Command` API. I tried
to be conservative with what went into the prelude modules, since it
might be hard/annoying to remove items from the prelude in the future.
Let me know if something should be included or excluded.

crates/nu-engine/src/call_ext.rs

@@ -1,13 +1,12 @@
-use nu_protocol::debugger::WithoutDebug;
+use crate::eval_expression;
 use nu_protocol::{
     ast::Call,
+    debugger::WithoutDebug,
     engine::{EngineState, Stack, StateWorkingSet},
     eval_const::eval_constant,
     FromValue, ShellError, Value,
 };
 
-use crate::eval_expression;
-
 pub trait CallExt {
     /// Check if a boolean flag is set (i.e. `--bool` or `--bool=true`)
     fn has_flag(

crates/nu-engine/src/command_prelude.rs

@@ -0,0 +1,7 @@
+pub use crate::CallExt;
+pub use nu_protocol::{
+    ast::{Call, CellPath},
+    engine::{Command, EngineState, Stack},
+    record, Category, Example, IntoInterruptiblePipelineData, IntoPipelineData, IntoSpanned,
+    PipelineData, Record, ShellError, Signature, Span, Spanned, SyntaxShape, Type, Value,
+};

crates/nu-engine/src/documentation.rs

@@ -1,15 +1,13 @@
-use nu_protocol::ast::{Argument, Expr, Expression, RecordItem};
-use nu_protocol::debugger::WithoutDebug;
+use crate::eval_call;
 use nu_protocol::{
-    ast::Call,
+    ast::{Argument, Call, Expr, Expression, RecordItem},
+    debugger::WithoutDebug,
     engine::{EngineState, Stack},
     record, Category, Example, IntoPipelineData, PipelineData, Signature, Span, SyntaxShape, Type,
     Value,
 };
 use std::{collections::HashMap, fmt::Write};
 
-use crate::eval_call;
-
 pub fn get_full_help(
     sig: &Signature,
     examples: &[Example],

crates/nu-engine/src/env.rs

@@ -1,15 +1,16 @@
-use std::collections::HashMap;
-use std::path::{Path, PathBuf};
-use std::sync::Arc;
-
-use nu_protocol::ast::{Call, Expr};
-use nu_protocol::engine::{EngineState, Stack, StateWorkingSet, PWD_ENV};
-use nu_protocol::{Config, PipelineData, ShellError, Span, Value, VarId};
-
-use nu_path::canonicalize_with;
-use nu_protocol::debugger::WithoutDebug;
-
 use crate::eval_block;
+use nu_path::canonicalize_with;
+use nu_protocol::{
+    ast::{Call, Expr},
+    debugger::WithoutDebug,
+    engine::{EngineState, Stack, StateWorkingSet, PWD_ENV},
+    Config, PipelineData, ShellError, Span, Value, VarId,
+};
+use std::{
+    collections::HashMap,
+    path::{Path, PathBuf},
+    sync::Arc,
+};
 
 #[cfg(windows)]
 const ENV_PATH_NAME: &str = "Path";

crates/nu-engine/src/eval.rs

@@ -1,18 +1,17 @@
-use std::{borrow::Cow, fs::OpenOptions, path::PathBuf};
-
 use crate::{current_dir, current_dir_str, get_config, get_full_help};
 use nu_path::expand_path_with;
-use nu_protocol::debugger::DebugContext;
 use nu_protocol::{
     ast::{
         Assignment, Block, Call, Expr, Expression, ExternalArgument, PathMember, PipelineElement,
         PipelineRedirection, RedirectionSource, RedirectionTarget,
     },
+    debugger::DebugContext,
     engine::{Closure, EngineState, Redirection, Stack},
     eval_base::Eval,
     Config, FromValue, IntoPipelineData, IoStream, PipelineData, ShellError, Span, Spanned, Type,
     Value, VarId, ENV_VARIABLE_ID,
 };
+use std::{borrow::Cow, fs::OpenOptions, path::PathBuf};
 
 pub fn eval_call<D: DebugContext>(
     engine_state: &EngineState,

crates/nu-engine/src/eval_helpers.rs

@@ -2,10 +2,12 @@ use crate::{
     eval_block, eval_block_with_early_return, eval_expression, eval_expression_with_input,
     eval_subexpression,
 };
-use nu_protocol::ast::{Block, Expression};
-use nu_protocol::debugger::{WithDebug, WithoutDebug};
-use nu_protocol::engine::{EngineState, Stack};
-use nu_protocol::{PipelineData, ShellError, Value};
+use nu_protocol::{
+    ast::{Block, Expression},
+    debugger::{WithDebug, WithoutDebug},
+    engine::{EngineState, Stack},
+    PipelineData, ShellError, Value,
+};
 
 /// Type of eval_block() function
 pub type EvalBlockFn =

crates/nu-engine/src/glob_from.rs

@@ -1,12 +1,11 @@
+use nu_glob::MatchOptions;
+use nu_path::{canonicalize_with, expand_path_with};
+use nu_protocol::{NuGlob, ShellError, Span, Spanned};
 use std::{
     fs,
     path::{Component, Path, PathBuf},
 };
 
-use nu_glob::MatchOptions;
-use nu_path::{canonicalize_with, expand_path_with};
-use nu_protocol::{NuGlob, ShellError, Span, Spanned};
-
 const GLOB_CHARS: &[char] = &['*', '?', '['];
 
 /// This function is like `nu_glob::glob` from the `glob` crate, except it is relative to a given cwd.

crates/nu-engine/src/lib.rs

@@ -1,5 +1,6 @@
 mod call_ext;
 pub mod column;
+pub mod command_prelude;
 pub mod documentation;
 pub mod env;
 mod eval;

crates/nu-engine/src/scope.rs

@@ -3,8 +3,7 @@ use nu_protocol::{
     engine::{Command, EngineState, Stack, Visibility},
     record, ModuleId, Signature, Span, SyntaxShape, Type, Value,
 };
-use std::cmp::Ordering;
-use std::collections::HashMap;
+use std::{cmp::Ordering, collections::HashMap};
 
 pub struct ScopeData<'e, 's> {
     engine_state: &'e EngineState,