History, more test coverage improvements, and refactorings. (#3217)

Improvements overall to Nu. Also among the changes here, we can also be more confident towards incorporating `3041`. End to end tests for checking envs properly exported to externals is not added here (since it's in the other PR)

A few things added in this PR (probably forgetting some too)

* no writes happen to history during test runs.
* environment syncing end to end coverage added.
* clean up / refactorings few areas.
* testing API for finer control (can write tests passing more than one pipeline)
* can pass environment variables in tests that nu will inherit when running.

* No longer needed.

* no longer under a module. No need to use super.

crates/nu-command/src/commands/config/command.rs

@@ -2,7 +2,7 @@ use crate::prelude::*;
 use nu_engine::CommandArgs;
 use nu_engine::WholeStreamCommand;
 use nu_errors::ShellError;
-use nu_protocol::{ReturnSuccess, Signature, UntaggedValue};
+use nu_protocol::{Primitive, ReturnSuccess, Signature, UntaggedValue, Value};
 use nu_stream::OutputStream;
 
 pub struct Command;
@@ -22,9 +22,16 @@ impl WholeStreamCommand for Command {
     }
 
     async fn run(&self, args: CommandArgs) -> Result<OutputStream, ShellError> {
-        let name_span = args.call_info.name_tag.clone();
-        let name = args.call_info.name_tag;
-        let result = nu_data::config::read(name_span, &None)?;
+        let name = args.call_info.name_tag.clone();
+
+        let path = match args.scope.get_var("config-path") {
+            Some(Value {
+                value: UntaggedValue::Primitive(Primitive::FilePath(path)),
+                ..
+            }) => Some(path),
+            _ => nu_data::config::default_path().ok(),
+        };
+        let result = nu_data::config::read(&name, &path)?;
 
         Ok(futures::stream::iter(vec![ReturnSuccess::value(
             UntaggedValue::Row(result.into()).into_value(name),