add: support for ruff as a Python linter and fixer (#4347)

this commit adds ruff as both a Python linter and fixer, together with
some tests and documentation.

ruff repo: https://github.com/charliermarsh/ruff

doc/ale-python.txt

@@ -1115,6 +1115,69 @@ g:ale_python_reorder_python_imports_use_global
   See |ale-integrations-local-executables|
 
 
+===============================================================================
+ruff                                                          *ale-python-ruff*
+
+g:ale_python_ruff_change_directory         *g:ale_python_ruff_change_directory*
+                                           *b:ale_python_ruff_change_directory*
+  Type: |Number|
+  Default: `1`
+
+  If set to `1`, `ruff` will be run from a detected project root, per
+  |ale-python-root|. if set to `0` or no project root detected,
+  `ruff` will be run from the buffer's directory.
+
+
+g:ale_python_ruff_executable                     *g:ale_python_ruff_executable*
+                                                 *b:ale_python_ruff_executable*
+  Type: |String|
+  Default: `'ruff'`
+
+  See |ale-integrations-local-executables|
+
+  Set this to `'pipenv'` to invoke `'pipenv` `run` `ruff'`.
+  Set this to `'poetry'` to invoke `'poetry` `run` `ruff'`.
+
+
+g:ale_python_ruff_options                           *g:ale_python_ruff_options*
+                                                    *b:ale_python_ruff_options*
+  Type: |String|
+  Default: `''`
+
+  This variable can be changed to add command-line arguments to the ruff
+  invocation.
+
+  For example, to select/enable and/or disable some error codes,
+  you may want to set >
+  let g:ale_python_ruff_options = '--ignore F401'
+
+
+g:ale_python_ruff_use_global                     *g:ale_python_ruff_use_global*
+                                                 *b:ale_python_ruff_use_global*
+  Type: |Number|
+  Default: `get(g:, 'ale_use_global_executables', 0)`
+
+  See |ale-integrations-local-executables|
+
+
+g:ale_python_ruff_auto_pipenv                   *g:ale_python_ruff_auto_pipenv*
+                                                *b:ale_python_ruff_auto_pipenv*
+  Type: |Number|
+  Default: `0`
+
+  Detect whether the file is inside a pipenv, and set the executable to `pipenv`
+  if true. This is overridden by a manually-set executable.
+
+
+g:ale_python_ruff_auto_poetry                   *g:ale_python_ruff_auto_poetry*
+                                                *b:ale_python_ruff_auto_poetry*
+  Type: |Number|
+  Default: `0`
+
+  Detect whether the file is inside a poetry, and set the executable to `poetry`
+  if true. This is overridden by a manually-set executable.
+
+
 ===============================================================================
 unimport                                                  *ale-python-unimport*
 

doc/ale-supported-languages-and-tools.txt

@@ -483,6 +483,7 @@ Notes:
   * `pyre`
   * `pyright`
   * `reorder-python-imports`
+  * ruff
   * `unimport`
   * `vulture`!!
   * `yapf`

doc/ale.txt

@@ -3160,6 +3160,7 @@ documented in additional help files.
     pyre..................................|ale-python-pyre|
     pyright...............................|ale-python-pyright|
     reorder-python-imports................|ale-python-reorder_python_imports|
+    ruff..................................|ale-python-ruff|
     unimport..............................|ale-python-unimport|
     vulture...............................|ale-python-vulture|
     yapf..................................|ale-python-yapf|