gh-106259: add minimal help target to Makefile

Doc/using/configure.rst

@@ -987,32 +987,99 @@ Main build steps
 Main Makefile targets
 ---------------------
 
-* ``make``: Build Python with the standard library.
-* ``make platform:``: build the ``python`` program, but don't build the
-  standard library extension modules.
-* ``make profile-opt``: build Python using Profile Guided Optimization (PGO).
-  You can use the configure :option:`--enable-optimizations` option to make
-  this the default target of the ``make`` command (``make all`` or just
-  ``make``).
-
-* ``make test``: Build Python and run the Python test suite with ``--fast-ci``
-  option. Variables:
-
-  * ``TESTOPTS``: additional regrtest command line options.
-  * ``TESTPYTHONOPTS``: additional Python command line options.
-  * ``TESTTIMEOUT``: timeout in seconds (default: 20 minutes).
-
-* ``make buildbottest``: Similar to ``make test``, but use ``--slow-ci``
-  option and default timeout of 20 minutes, instead of ``--fast-ci`` option
-  and a default timeout of 10 minutes.
-
-* ``make install``: Build and install Python.
-* ``make regen-all``: Regenerate (almost) all generated files;
-  ``make regen-stdlib-module-names`` and ``autoconf`` must be run separately
-  for the remaining generated files.
-* ``make clean``: Remove built files.
-* ``make distclean``: Same than ``make clean``, but remove also files created
-  by the configure script.
+make [all]
+^^^^^^^^^^
+
+For the most part, when rebuilding after editing some code or
+refreshing your checkout from upstream, all you need to do is execute
+``make``, which (per Make's semantics) builds the default target, the
+first one defined in the Makefile.  By tradition (including in the
+CPython project) this is usually the ``all`` target. The
+``configure`` script expands an ``autoconf`` variable,
+``@DEF_MAKE_ALL_RULE@`` to describe precisely which targets ``make
+all`` will build. The three choices are
+
+* ``profile-opt`` (configured with ``--enable-optimizations``)
+* ``build_wasm`` (configured with ``--with-emscripten-target``)
+* ``build_all`` (configured without explicitly using either of the others)
+
+Depending on the most recent source file changes, Make will rebuild
+any targets (object files and executables) deemed out-of-date,
+including running ``configure`` again if necessary, Source/target
+dependencies are many and maintained manually however, so Make
+sometimes doesn't have all the information necessary to correctly
+detect all targets which need to be rebuilt.  Depending on which
+targets aren't rebuilt, you might experience a number of problems. If
+you have build or test problems which you can't otherwise explain,
+``make clean && make`` should work around most dependency problems, at
+the expense of longer build times.
+
+
+make platform
+^^^^^^^^^^^^^
+
+Build the ``python`` program, but don't build the standard library
+extension modules. This generates a file named ``platform`` which
+contains a single line describing the details of the build platform,
+e.g., ``macosx-14.3-arm64-3.12`` or ``linux-x86_64-3.13``.
+
+
+make profile-opt
+^^^^^^^^^^^^^^^^
+
+Build Python using Profile Guided Optimization (PGO).  You can use the
+configure :option:`--enable-optimizations` option to make this the
+default target of the ``make`` command (``make all`` or just
+``make``).
+
+
+
+make clean
+^^^^^^^^^^
+
+Remove built files.
+
+
+make distclean
+^^^^^^^^^^^^^^
+
+In addition to the the work done by ``make clean``, remove files
+created by the configure script.  ``configure`` will have to be run
+before building again. [#]_
+
+
+make install
+^^^^^^^^^^^^
+
+Build the ``all`` target and install Python.
+
+
+make test
+^^^^^^^^^
+
+Build the ``all`` target and run the Python test suite with the
+``--fast-ci`` option. Variables:
+
+* ``TESTOPTS``: additional regrtest command line options.
+* ``TESTPYTHONOPTS``: additional Python command line options.
+* ``TESTTIMEOUT``: timeout in seconds (default: 10 minutes).
+
+
+make buildbottest
+^^^^^^^^^^^^^^^^^
+
+This is similar to ``make test``, but uses the ``--slow-ci``
+option and default timeout of 20 minutes, instead of ``--fast-ci`` option.
+
+
+make regen-all
+^^^^^^^^^^^^^^
+
+Regenerate (almost) all generated files. These include (but are not
+limited to) bytecode cases, parser generator files, and SBOM file.
+``make regen-stdlib-module-names`` and ``autoconf`` must be run
+separately for the remaining generated files.
+
 
 C extensions
 ------------
@@ -1303,3 +1370,13 @@ Linker flags
    Linker flags used for building the interpreter object files.
 
    .. versionadded:: 3.8
+
+
+.. rubric:: Footnotes
+
+.. [#] ``git clean -fdx`` removes all files not known to Git.
+   When bug hunting using ``git bisect``, this is
+   `recommended between probes <https://github.com/python/cpython/issues/114505#issuecomment-1907021718>`_
+   to guarantee a completely clean build. **Use with care**, as it
+   will delete all files not checked into Git, including your
+   uncommitted work.

Makefile.pre.in

@@ -646,6 +646,20 @@ all:		@DEF_MAKE_ALL_RULE@
 # all.
 .PHONY: all
 
+# Provide quick help for common Makefile targets.
+.PHONY: help
+help:
+	@echo "Please use \`make <target>' where <target> is one of"
+	@echo "  clean      to remove build files"
+	@echo "  distclean  'clean' + remove other generated files (patch, exe, etc)"
+	@echo "  clinic     run Argument Clinic over source files"
+	@echo "  install    install built files"
+	@echo "  recheck    rerun configure with last cmdline options"
+	@echo "  regen-all  regenerate a number of generated source files"
+	@echo "  reindent   reindent .py files in Lib directory"
+	@echo "  tags       build a tags file (useful for Emacs and other editors)"
+	@echo "  test       run the test suite"
+
 .PHONY: build_all
 build_all:	check-clean-src $(BUILDPYTHON) platform sharedmods \
 		gdbhooks Programs/_testembed scripts checksharedmods rundsymutil