Same rationale as in #4378
Also accelerate `grid`
before:
```
Command being timed: "./eager_nu -c for i in 0..100000 { echo whatever } | grid"
User time (seconds): 0.21
System time (seconds): 0.05
Percent of CPU this job got: 36%
Elapsed (wall clock) time (h:mm:ss or m:ss): 0:00.71
Average shared text size (kbytes): 0
Average unshared data size (kbytes): 0
Average stack size (kbytes): 0
Average total size (kbytes): 0
Maximum resident set size (kbytes): 48112
Average resident set size (kbytes): 0
Major (requiring I/O) page faults: 0
Minor (reclaiming a frame) page faults: 10580
Voluntary context switches: 266
Involuntary context switches: 2595
Swaps: 0
File system inputs: 0
File system outputs: 0
Socket messages sent: 0
Socket messages received: 0
Signals delivered: 0
Page size (bytes): 4096
Exit status: 0
```
after:
```
Command being timed: "./lazy_nu -c for i in 0..100000 { echo whatever } | grid"
User time (seconds): 0.14
System time (seconds): 0.05
Percent of CPU this job got: 33%
Elapsed (wall clock) time (h:mm:ss or m:ss): 0:00.60
Average shared text size (kbytes): 0
Average unshared data size (kbytes): 0
Average stack size (kbytes): 0
Average total size (kbytes): 0
Maximum resident set size (kbytes): 48272
Average resident set size (kbytes): 0
Major (requiring I/O) page faults: 1
Minor (reclaiming a frame) page faults: 10582
Voluntary context switches: 286
Involuntary context switches: 831
Swaps: 0
File system inputs: 56
File system outputs: 0
Socket messages sent: 0
Socket messages received: 0
Signals delivered: 0
Page size (bytes): 4096
Exit status: 0
```
* Use only $nu.env.PWD for getting current directory
Because setting and reading to/from std::env changes the global state
shich is problematic if we call `cd` from multiple threads (e.g., in a
`par-each` block).
With this change, when engine-q starts, it will either inherit existing
PWD env var, or create a new one from `std::env::current_dir()`.
Otherwise, everything that needs the current directory will get it from
`$nu.env.PWD`. Each spawned external command will get its current
directory per-process which should be thread-safe.
One thing left to do is to patch nu-path for this as well since it uses
`std::env::current_dir()` in its expansions.
* Rename nu-path functions
*_with is not *_relative which should be more descriptive and frees
"with" for use in a followup commit.
* Clone stack every each iter; Fix some commands
Cloning the stack each iteration of `each` makes sure we're not reusing
PWD between iterations.
Some fixes in commands to make them use the new PWD.
* Post-rebase cleanup, fmt, clippy
* Change back _relative to _with in nu-path funcs
Didn't use the idea I had for the new "_with".
* Remove leftover current_dir from rebase
* Add cwd sync at merge_delta()
This makes sure the parser and completer always have up-to-date cwd.
* Always pass absolute path to glob in ls
* Do not allow PWD a relative path; Allow recovery
Makes it possible to recover PWD by proceeding with the REPL cycle.
* Clone stack in each also for byte/string stream
* (WIP) Start moving env variables to engine state
* (WIP) Move env vars to engine state (ugly)
Quick and dirty code.
* (WIP) Remove unused mut and args; Fmt
* (WIP) Fix dataframe tests
* (WIP) Fix missing args after rebase
* (WIP) Clone only env vars, not the whole stack
* (WIP) Add env var clone to `for` loop as well
* Minor edits
* Refactor merge_delta() to include stack merging.
Less error-prone than doing it manually.
* Clone env for each `update` command iteration
* Mark env var hidden only when found in eng. state
* Fix clippt warnings
* Add TODO about env var reading
* Do not clone empty environment in loops
* Remove extra cwd collection
* Split current_dir() into str and path; Fix autocd
* Make completions respect PWD env var
* get_columns is working in the columns command
* the new location of the get_columns method is nu-protocol/src/column.rs
* reference the new location of the get_columns method
* move get_columns to nu-engine
* Proof of concept treating env vars as Values
* Refactor env var collection and method name
* Remove unnecessary pub
* Move env translations into a new file
* Fix LS_COLORS to support any Value
* Fix spans during env var translation
* Add span to env var in cd
* Improve error diagnostics
* Fix non-string env vars failing string conversion
* Make PROMPT_COMMAND a Block instead of String
* Record host env vars to a fake file
This will give spans to env vars that would otherwise be without one.
Makes errors less confusing.
* Add 'env' command to list env vars
It will list also their values translated to strings
* Sort env command by name; Add env var type
* Remove obsolete test
* add icons to grid output. still needs cleanup
* working but adds a dependency on ansi_term - need to fix that
* update styling, added lots of green code to icons
* clippy
* add config point for grid icons
* option to replace command same name
* moved order of custom value declarations
* arranged dataframe folders and objects
* sort help commands by name
* added dtypes function for debugging
* corrected name for dataframe commands
* command names using function
* custom value trait
* functions for custom value trait
* custom trait behind flag
* open dataframe command
* command to-df for basic types
* follow path for dataframe
* dataframe operations
* dataframe not default feature
* custom as default feature
* corrected examples in command
