Rework the 'make -n -n' feature such that '-n' recurses and '-N' does not.

Bmake has a documented feature of '-N' to skip executing commands which is
specifically intended for debugging top-level builds and not recursing into
sub-directories.  This matches the older 'make -n' behavior we added which made
'-n -n' the recursing target and '-n' a non-recursing target.

Removing the '-n -n' feature allows the build to work as documented in
the bmake manpage with '-n' and '-N'.  The older '-n -n' feature was also
not documented anywhere that I could see.

Note that the ${_+_} var is still needed as currently bmake incorrectly
executes '+' commands when '-N' is specified.

The '-n' and '-n -n' features were broken for several reasons prior to this.
r251748 made '_+_' never expand with '-n -n' which resulted in many
sub-directories not being visited until fixed 2 years later in r288391, and
many targets were given .MAKE over the past few years which resulted in
non-sub-make commands, such as rm and ln and mtree, to be executed.

This should also allow removing some indirection hacks in bsd.subdir.mk and
other cases of .USE that have a .MAKE by using '+'.

Sponsored by:	EMC / Isilon Storage Division
Discussed on:	arch@ (mostly silence)

3 files changed, 13 insertions, 14 deletions

diff --git a/Makefile b/Makefile
index c3326b7ddc43..130fdbf67200 100644
--- a/Makefile
+++ b/Makefile
@@ -243,14 +243,8 @@ cleanworld:
 # Handle the user-driven targets, using the source relative mk files.
 #
 
-.if !(!empty(.MAKEFLAGS:M-n) && ${.MAKEFLAGS:M-n} == "-n")
-# skip this for -n to avoid changing previous behavior of 
-# 'make -n buildworld' etc.  Using -n -n will run it.
-${TGTS}: .MAKE
 tinderbox toolchains kernel-toolchains: .MAKE
-.endif
-
-${TGTS}: .PHONY
+${TGTS}: .PHONY .MAKE
 	${_+_}@cd ${.CURDIR}; ${_MAKE} ${.TARGET}
 
 # The historic default "all" target creates files which may cause stale
diff --git a/UPDATING b/UPDATING
index baff1f13605b..1095ba6ea5d1 100644
--- a/UPDATING
+++ b/UPDATING
@@ -31,6 +31,12 @@ NOTE TO PEOPLE WHO THINK THAT FreeBSD 11.x IS SLOW:
 	disable the most expensive debugging functionality run
 	"ln -s 'abort:false,junk:false' /etc/malloc.conf".)
 
+20151017:
+	The build previously allowed using 'make -n' to not recurse into
+	sub-directories while showing what commands would be executed, and
+	'make -n -n' to recursively show commands.  Now 'make -n' will recurse
+	and 'make -N' will not.
+
 20151012:
 	If you specify SENDMAIL_MC or SENDMAIL_CF in make.conf, mergemaster
 	and etcupdate will now use this file. A custom sendmail.cf is now
diff --git a/share/mk/sys.mk b/share/mk/sys.mk
index e8f4892cd99d..b6c75b6f96a6 100644
--- a/share/mk/sys.mk
+++ b/share/mk/sys.mk
@@ -145,13 +145,12 @@ ECHODIR		?=	true
 .endif
 .endif
 
-.if defined(.PARSEDIR)
-# _+_ appears to be a workaround for the special src .MAKE not working.
-# setting it to + interferes with -N
-_+_		?=
-.elif !empty(.MAKEFLAGS:M-n) && ${.MAKEFLAGS:M-n} == "-n"
-# the check above matches only a single -n, so -n -n will result
-# in _+_ = +
+.if ${.MAKEFLAGS:M-N}
+# bmake -N is supposed to skip executing anything but it does not skip
+# exeucting '+' commands.  The '+' feature is used where .MAKE
+# is not safe for the entire target.  -N is intended to skip building sub-makes
+# so it executing '+' commands is not right.  Work around the bug by not
+# setting '+' when -N is used.
 _+_		?=
 .else
 _+_		?=	+