### Motivation
* We have no recommended way to force subprocess command be
(un)threadable
* #4214
* #2119
* #5003
* It's interesting opportunity to have a way to modify specs and CP
using `SpecModifierAlias`.
### Before
```xsh
!(ssh host -T "echo 1")
# output='' # EXPECTED: 1
__xonsh__.commands_cache.threadable_predictors['ssh'] = lambda *a, **kw: True
!(ssh host -T "echo 1")
```
### After
```xsh
xthread
# Mark command as threadable.
!(xthread ssh host -T "echo 1")
# output='1'
```
Closes:
* Closes#4214
* Closes#2119
* Partially closes#5003
Implementation of `SpecModifierAlias` will help in:
* #2618
JFYI #5413
## For community
⬇️ **Please click the 👍 reaction instead of leaving a `+1` or 👍
comment**
---------
Co-authored-by: a <1@1.1>
Co-authored-by: pre-commit-ci[bot] <66853113+pre-commit-ci[bot]@users.noreply.github.com>
Co-authored-by: Gil Forsyth <gforsyth@users.noreply.github.com>
* add "disown" internal command
This command will remove jobs from the shell's job table, allowing the command
to continue running after the shell exits. Configuration options are provided
to manage how suspended background jobs are handled after being disowned.
* job-ctrl-disown code style update
* job-ctrl-disown style updates + change arg --cont to --continue
* Trim extra "=" in doc for "disown" cmd
Co-authored-by: Gil Forsyth <gforsyth@users.noreply.github.com>
Co-authored-by: Gil Forsyth <gforsyth@users.noreply.github.com>
* First attempt at register/deregister machinery for envvars
* Added detailed docstring, simplified ensurers
Also added some type checking that became clear from docstring writing.
* Changes in response to @scopatz review
Simplified kwarg names.
* defaultval -> default
* Created new Var namedtuple, as well as DEFAULT_VARS
We should now delete DEFAULT_ENSURERS, DEFAULT_VALUES, DEFAULT_DOCS, and
refactor Env to use the new single namedtuple and the DEFAULT_VARS dict
* Removed DEFAULT_ENSURERS, DEFAULT_VALUES, DEFAULT_DOCS
Now need to edit Env to use new DEFAULT_VARS, Var namedtuple
* Finished updating Env object to use new combined Var
Also made corresponding changes elsewhere ensurer was used
* Working on test failures
* More fixes in light of test failures
* Set default values for Var in register.
There's a bit of duplication here, but makes for a cleaner function.
* Black reformatting on environ.py
* Removed history replay
* Added register tests
* Added addtional deregistration test
* Removed all replay references, in docs too
* Added news item for env-reg-dereg
* trigger rebuild
* doc fix
* more doc fixes
* again
* attr names
* reorder imports
* fix flake error
Co-authored-by: Anthony Scopatz <scopatz@gmail.com>
