doc/Makefile: Allow to create and use .venv

Add 'setup' target (alias to '.venv') to create virtualenv directory.
This is an optional target (not run by default).
If .venv exists, it's used in other targets, activation supports only
fish and bash/zsh (known shells used by LTP developers, csh/tcsh is
ignored atm).

This helps to use virtualenv for development, but avoid using it by
default (readthedoc uses container with virtualenv, creating it would be
waste of time).

Add 'distclean' target which removes also .venv/ directory.

Link: https://lore.kernel.org/ltp/20250407150133.115790-4-pvorel@suse.cz/
Reviewed-by: Andrea Cervesato <andrea.cervesato@suse.com>
Signed-off-by: Petr Vorel <pvorel@suse.cz>

Author: pevik

doc/Makefile

@@ -5,15 +5,33 @@ top_srcdir		?= ..
 
 include $(top_srcdir)/include/mk/env_pre.mk
 
+PYTHON := python3
+VENV_DIR := .venv
+
+# only fish and bash/zsh supported
+VENV_CMD := if [ "x${FISH_VERSION}" != "x" ]; then . $(VENV_DIR)/bin/activate.fish; else . $(VENV_DIR)/bin/activate; fi
+
+RUN_VENV := if [ -d $(VENV_DIR) ]; then $(VENV_CMD); fi
+
+$(VENV_DIR):
+	$(PYTHON) -m virtualenv $(VENV_DIR)
+	$(VENV_CMD) && pip install -r requirements.txt
+
+.PHONY: setup
+setup: $(VENV_DIR)
+
 ${abs_top_builddir}/metadata/ltp.json:
 	$(MAKE) -C ${abs_top_builddir}/metadata
 
 all: ${abs_top_builddir}/metadata/ltp.json
-	sphinx-build -b html . html
+	$(RUN_VENV); sphinx-build -b html . html
 
 spelling:
-	sphinx-build -b spelling -d build/doctree . build/spelling
+	$(RUN_VENV); sphinx-build -b spelling -d build/doctree . build/spelling
 
 clean:
 	rm -rf html/ build/ _static/syscalls.rst _static/tests.rst syscalls.tbl \
 		${abs_top_builddir}/metadata/ltp.json
+
+distclean: clean
+	rm -rf $(VENV_DIR)