* src/variable.c (defined_vars): Add GNUMAKEFLAGS to defined variables.
* tests/scripts/options/warn: Add a test.

Disable builtin variables and rules immediately, when -R or -r is
added to MAKEFLAGS inside the makefile.

* src/main.c (disable_builtins): Add new function disable_builtins().
(main): Call disable_builtins().
(reset_makeflags): Call disable_builtins().
* tests/scripts/options/dash-r: Add tests.
* tests/scripts/variables/MAKEFLAGS: Update tests.

Avoid cross-contamination between test files by creating a new
working directory for each file, and setting it as the current
directory before starting the tests in that file.

Rename the test output as tNNN.{base,log,diff,mk} where NNN is
a test number starting with 001 for the first test.  It is
slightly more annoying to find diff files since you can't use
autocomplete directly but it is simpler to match things.

Detect the source directory as the location of the test_driver.pl
script, so remove the separate -srcdir option.

* Makefile.am: Remove hacks to create symlinks when building
out-of-tree, and remove -srcdir option from run_make_tests.
* tests/test_driver.pl: Locate $srcpath based on __FILE__, then
compute $toppath as its parent.  Set $scriptpath under $srcpath
and $workpath under the current directory.  Toss $*_filename
and modify get_logfile() etc. to use the suffix directly.  Add
a chdir() around the invocation of the test.
* tests/run_make_tests.pl: Throw out the -srcdir option and use
$srcpath set in test_driver.pl.  The #WORK# helper is no longer
useful so remove it.  Set #PWD# to the current working dir. Always
search the local directory and $srcpath for config-flags.pm.
Use $srcpath for finding the thelp.pl script.
* tests/scripts/features/vpath: Don't put things in work/ as it
is no longer a subdirectory.
* tests/scripts/features/vpathgpath: Ditto.
* tests/scripts/features/vpathplus: Ditto.
* tests/scripts/misc/general1: Ditto.
* tests/scripts/misc/general2: Ditto.
* tests/scripts/options/dash-k: Ditto.
* tests/scripts/options/symlinks: Use $testpath as the working
directory.
* tests/scripts/variables/GNUMAKEFLAGS: Use the test helper to
display env var values (grepping for GNUMAKEFLAGS finds extra things
now that it is our current working directory).

Change error and fatal messages to start with lowercase and not
end with a period.  Note a few very common messages were left
as-is, just in case some other tools parse them.

Also modify the test known-good-output to satisfy the messages.

Create a new special variable, .WARNINGS, to allow per-makefile
control over warnings.  The command line settings will override
this.

Move the handling of warning flags to a new file: src/warning.c.
Allow the decode to work with generic strings, and call it from
decode_switches().

* Makefile.am: Add new file src/warning.c.
* build_w32.bat: Ditto.
* builddos.bat: Ditto.
* po/POTFILES.in: Ditto.
* src/makeint.h: #define for the .WARNINGS variable name.
* src/warning.h: Add declarations for methods moved from main.c.
Rename the enum warning_state to warning_action.
* src/warning.c: New file.  Move all warning encode/decode here
from main.c.
* src/main.c: Move methods into warning.c and call those methods
instead.
(main): Set .WARNINGS as a special variable.
* src/job.c (construct_command_argv): Rename to warning_action.
* src/read.c (tilde_expand): Ditto.
* src/variable.c (set_special_var): Update warnings when the
.WARNINGS special variable is set.
* tests/scripts/options/warn: Check invalid warning options.
* tests/scripts/variables/WARNINGS: Add tests for the .WARNINGS
special variable.

The "invalid-var" warning triggers if the makefile attempts to assign
a value to an invalid variable name (a name containing whitespace).
The "invalid-ref" warning triggers if the makefile attempts to
reference an invalid variable name.  Both new warnings have a default
action of "warn".

* NEWS: Add these new warnings.
* doc/make.1: Document them in the man page.
* doc/make.texi (Warnings): Document them in the user's manual.
* src/warning.h: Add enum values for the new warning types.
* src/main.c (initialize_warnings): Initialize the new warnings.
* src/variable.h (undefine_variable_in_set, undefine_variable_global):
Ask callers to provide a struct floc specifying where the variable
is undefined.
* src/read.c (do_undefine): Pass floc when undefining.
* src/variable.c (check_valid_name): If invalid-var is enabled, check
the variable name.
(define_variable_in_set): Call it.
(undefine_variable_in_set): Ditto.
(check_variable_reference): If invalid-ref is enabled, check the
variable reference.
(lookup_variable): Call it.
(lookup_variable_in_set): Ditto.
* tests/scripts/options/warn: Add tests for the new warning types.

Replace the singleton --warn-undefined-variables with infrastructure
to manage multiple warnings: the --warn option can take an action
"ignore", "warn", or "error" (which will apply to all warnings), or
a specific warning type and an action for that type.  Multiple
options can be provided and are consolidated.

* NEWS: Announce the new option.
* doc/make.1: Document in the man page.
* doc/make.texi (Warnings): Document in the user's manual.
* Makefile.am: Add new header warning.h.
* src/warning.h: Define enum for actions and warning types, and
macros to test whether they are set.  Keep the default settings
separate so that we can correctly reconstruct MAKEFLAGS.
* src/makeint.h: Remove deprecated warn_undefined_variables_flag.
* src/main.c: Create global variables to hold warning settings.
(switches): Add a new switch for --warn.
(initialize_warnings): Set the default warning actions.
(main): Call initialize_warnings().
(encode_warning_state, decode_warning_state): Convert warning states
between strings and enums.
(encode_warning_name, decode_warning_name): Convert warning names
between strings and enums.
(decode_warn_flags): Convert a --warn option into enum values.  If
deprecated warn_undefined_variables_flag is set convert it to --warn.
(decode_switches): Don't remove duplicates of --warn since order
matters.  Call decode_warn_flags() to handle --warn.
(define_makeflags): Special-case handling of --warn options written
to MAKEFLAGS: write out the current settings.
* src/read.c (tilde_expand): Use new warning control macros.
* src/variable.c (warn_undefined): Ditto.
* src/job.c (construct_command_argv): Ditto.
* tests/scripts/options/warn: Rename from warn-undefined-variables
and add tests for --warn.
* tests/scripts/variables/MAKEFLAGS: Expect the new behavior.

* tests/thelp.pl: Add "exist" and "noexist" operators.

* tests/scripts/features/temp_stdin: Ditto.
* tests/scripts/options/dash-f: Ditto.

If -e was given we weren't expanding MAKEFLAGS before passing it
through the environment to jobs: we don't expand variables we
receive from the environment and when -e is given we set the
origin of MAKEFLAGS to "environment override".  Check for MAKEFLAGS
specifically, which seems like a hack but I don't have a better
idea offhand.

* src/main.c (main): Drive-by: use o_default for MAKEOVERRIDES.
* src/variable.c (target_environment): Always expand MAKEFLAGS
regardless of the origin type.
* tests/scripts/options/dash-e: Create a test.