Update codespell Docker image definition

.gitignore

@@ -9,6 +9,9 @@
 .tools/
 **/internal/test/e2e/*/main
 
+# Python pip cache.
+.cache/
+
 # Test binary, built with `go test -c`
 *.test
 

Makefile

@@ -20,6 +20,10 @@ export BPF2GO_CFLAGS
 GOCMD?= go
 CGO_ENABLED?=0
 
+# User to run as in docker images.
+DOCKER_USER=$(shell id -u):$(shell id -g)
+DEPENDENCIES_DOCKERFILE=./dependencies.Dockerfile
+
 .DEFAULT_GOAL := precommit
 
 .PHONY: precommit
@@ -249,11 +253,8 @@ PIP := $(PYTOOLS)/pip
 # The directory in the docker image where the current directory is mounted.
 WORKDIR := /workdir
 
-# Ensure correct ownership.
-DOCKER_USER=$(shell id -u):$(shell id -g)
-
 # The python image to use for the virtual environment.
-PYTHONIMAGE := python:3.11.3-slim-bullseye
+PYTHONIMAGE := $(shell awk '$$4=="python" {print $$2}' $(DEPENDENCIES_DOCKERFILE))
 
 # Run the python image with the current directory mounted.
 DOCKERPY := docker run --rm -u $(DOCKER_USER) -v "$(CURDIR):$(WORKDIR)" -w $(WORKDIR) $(PYTHONIMAGE)
@@ -262,11 +263,11 @@ DOCKERPY := docker run --rm -u $(DOCKER_USER) -v "$(CURDIR):$(WORKDIR)" -w $(WOR
 $(PYTOOLS):
 # The `--upgrade` flag is needed to ensure that the virtual environment is
 # created with the latest pip version.
-	@$(DOCKERPY) bash -c "python3 -m venv $(VENVDIR) && $(PIP) install --upgrade pip"
+	@$(DOCKERPY) bash -c "python3 -m venv $(VENVDIR) && $(PIP) install --upgrade --cache-dir=$(WORKDIR)/.cache/pip pip"
 
 # Install python packages into the virtual environment.
 $(PYTOOLS)/%: $(PYTOOLS)
-	@$(DOCKERPY) $(PIP) install -r requirements.txt
+	@$(DOCKERPY) $(PIP) install --cache-dir=$(WORKDIR)/.cache/pip -r requirements.txt
 
 CODESPELL = $(PYTOOLS)/codespell
 $(CODESPELL): PACKAGE=codespell

dependencies.Dockerfile

@@ -0,0 +1,2 @@
+# This is a renovate-friendly source of Docker images.
+FROM python:3.13.1-slim-bullseye AS python