build: unify docdir to doc_dir

Make it similar to test_dir and src_dir etc. Remove the unnecessary doc
variable while at it.

Makefile.local

@@ -2,8 +2,6 @@
 # Copyright (c) 2018, Jani Nikula <[email protected]>
 # Licensed under the terms of BSD 2-Clause, see LICENSE for details.
 
-dir := .
-
 RST := $(RST) CHANGELOG.rst CONTRIBUTING.rst README.rst
 
 # Static analysis

doc/Makefile.local

@@ -3,22 +3,19 @@
 # Makefile for Sphinx documentation
 #
 
-dir := doc
-
-# dir may get overwritten, make a copy
-docdir := $(dir)
+doc_dir := doc
 
 # You can set these variables from the command line, and also
 # from the environment for the first two.
 SPHINXOPTS    ?= -t use-installed-hawkmoth
 SPHINXBUILD   ?= sphinx-build
-SOURCEDIR     = $(docdir)
-BUILDDIR      = $(docdir)/_build
+SOURCEDIR     = $(doc_dir)
+BUILDDIR      = $(doc_dir)/_build
 
 CLEAN := $(CLEAN) $(BUILDDIR)
 
 update-examples:
-	$(test_dir)/update-examples.py > $(docdir)/examples.rst
+	$(test_dir)/update-examples.py > $(doc_dir)/examples.rst
 
 # Catch-all target: route all unknown targets to Sphinx using the new
 # "make mode" option.  $(O) is meant as a shortcut for $(SPHINXOPTS).

test/Makefile.local

@@ -14,7 +14,7 @@ test-verbose:
 
 # Ensure a) update-examples works, and b) examples have been updated.
 check-examples:
-	$(test_dir)/update-examples.py | diff -u $(docdir)/examples.rst -
+	$(test_dir)/update-examples.py | diff -u $(doc_dir)/examples.rst -
 
 quick-test:
 	pytest -n auto -m "not full"