[REF] refactor style checks in CI (#4406)

* refactor style checks in CI

* update doc

* misc

* fix

* ref

.github/workflows/README.md

@@ -21,12 +21,6 @@ Allows anyone to self-assign an issue automatically by commenting the word `take
 
 Automatically comments on a newly open pull request to provide some guidelines, useful links and a checklist. The checklist is only editable by maintainers at the moment.
 
-## Black formatting
-
-### black.yml
-
-Runs black code formatter on the codebase both in pull requests and on main. Configurations can be found in [pyproject.toml](../../pyproject.toml).
-
 ## Building the development documentation
 
 ### build-docs.yml
@@ -63,6 +57,9 @@ However for quick checks to do yourself you should always opt for local builds f
 
 Note: setuptools needs to be installed to run the doc build with python 3.12.
 
+Upon a successful build of the doc, it is zipped and uploaded as an artifact.
+A circle-ci workflow is then triggered. See below.
+
 #### Dataset caching
 
 We also implemented a dataset caching strategy within this Actions workflow such that datasets are only downloaded once every month.
@@ -78,10 +75,13 @@ To run a full build and download all datasets, you would then combine both tags:
 $ git commit -m "[full doc][force download] request full build"
 ```
 
-#### Hosting of the docs
+## Building the stable release documentation
 
-Upon a successful build of the doc, it is zipped and uploaded as an artifact.
-A circle-ci workflow is then triggered. See below.
+### release-docs.yml
+
+Should be triggered automatically after merging and tagging a release PR to
+build the stable docs with a GitHub runner and push to nilearn.github.io.
+Can also be triggered manually.
 
 ## Hosting and deploying development documentation
 
@@ -107,46 +107,12 @@ Pings github API to collect information about:
 Plots the results and saves it as an artefact to download and manually inspect
 to see if there is a trend in tests taking longer.
 
-## Check spelling errors
-
-### codespell.yml
-
-Checks for spelling errors. Configured in [pyproject.toml](../../pyproject.toml). More information here: https://github.com/codespell-project/actions-codespell
-
-## PEP8 check
+## Style checks
 
-### flake8.yml
+### check_style_guide.yml
 
-Uses flake8 tool to verify code is PEP8 compliant. Configured in [.flake8](../../.flake8)
-
-## f strings
-
-### f_strings.yml
-
-Checks for f strings in the codebase with [flynt](https:/pypi.org/project/flynt/).
-Configured in [pyproject.toml](../../pyproject.toml)
-Flynt will check if it automatically convert "format" or "%" strings to "f strings".
-This workflow will fail if it finds any potential target to be converted.
-
-## Prettier formatting
-
-### prettier.yml
-
-Runs prettier to format HTML and CSS on the codebase both in pull requests and on main.
-
-## Sort imports automatically
-
-### isort.yml
-
-Sorts Python imports alphabetically and by section. Configured in [pyproject.toml](../../pyproject.toml)
-
-## Building the stable release documentation
-
-### release-docs.yml
-
-Should be triggered automatically after merging and tagging a release PR to
-build the stable docs with a GitHub runner and push to nilearn.github.io.
-Can also be triggered manually.
+Relies on pre-commit to run a series of check on the content of the repositories.
+See the config [`.pre-commit-config.yaml`](../../.pre-commit-config.yaml).
 
 ## Running unit tests
 

.github/workflows/flake8.yml → .github/workflows/check_style_guide.yml

@@ -1,5 +1,5 @@
 ---
-name: flake8
+name: check style guide compliance
 
 on:
     push:
@@ -13,27 +13,27 @@ concurrency:
     group: ${{ github.workflow }}-${{ github.ref }}
     cancel-in-progress: true
 
+# Force to use color
+env:
+    FORCE_COLOR: true
+
 jobs:
-    flake8:
-        name: run flake8
+    style_check:
+        name: run pre-commit on all files
         runs-on: ubuntu-latest
 
-        defaults:
-            run:
-                shell: bash
-
         steps:
         -   name: Checkout nilearn
             uses: actions/checkout@v4
 
         -   name: Setup python
             uses: actions/setup-python@v5
             with:
-                python-version: '3.12'
+                python-version: '3.11'
                 allow-prereleases: false
 
         -   name: Install tox
             run: python -m pip install --upgrade tox
 
-        -   name: Run Flake8
-            run: tox run -e flake8
+        -   name: Run pre-commit via tox
+            run: tox