1 files changed, 71 insertions, 0 deletions
diff --git a/build-aux/Makefile.head.mk b/build-aux/Makefile.head.mk
new file mode 100644
index 0000000000..36c2c0a2e8
--- /dev/null
+++ b/build-aux/Makefile.head.mk
@@ -0,0 +1,71 @@
+# Copyright (C) 2015-2016  Luke Shumaker
+#
+# This program is free software: you can redistribute it and/or modify
+# it under the terms of the GNU Affero General Public License as published by
+# the Free Software Foundation, either version 3 of the License, or
+# (at your option) any later version.
+#
+# This program is distributed in the hope that it will be useful,
+# but WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+# GNU Affero General Public License for more details.
+#
+# You should have received a copy of the GNU Affero General Public License
+# along with this program.  If not, see <http://www.gnu.org/licenses/>.
+
+# This bit only gets evaluated once, at the very beginning
+ifeq ($(origin _at.NO_ONCE),undefined)
+
+ifeq ($(topsrcdir),)
+$(error topsrcdir must be set before including Makefile.head.mk)
+endif
+ifeq ($(topoutdir),)
+$(error topoutdir must be set before including Makefile.head.mk)
+endif
+
+_at.noslash = $(patsubst %/.,%,$(patsubst %/,%,$1))
+# These are all $(call _at.func,parent,child)
+#at.relto = $(if $2,$(shell realpath -sm --relative-to='$1' $2))
+_at.is_subdir = $(filter $(abspath $1)/%,$(abspath $2)/.)
+_at.relto_helper = $(if $(call _at.is_subdir,$1,$2),$(patsubst $1/%,%,$(addsuffix /.,$2)),$(addprefix ../,$(call _at.relto_helper,$(patsubst %/,%,$(dir $1)),$2)))
+_at.relto = $(call _at.noslash,$(call _at.relto_helper,$(call _at.noslash,$(abspath $1)),$(call _at.noslash,$(abspath $2))))
+at.relto = $(foreach p,$2,$(call _at.relto,$1,$p))
+# Note that _at.is_subdir says that a directory is a subdirectory of
+# itself.
+at.path = $(call at.relto,.,$1)
+
+_at.addprefix = $(if $(filter /%,$2),$2,$1/$2)
+at.addprefix = $(foreach f,$2, $(addsuffix $(if $(filter %/,$f),/),$(call at.path,$(call _at.addprefix,$1,$f)) ))
+
+define at.nl
+
+
+endef
+
+at.Makefile ?= Makefile
+
+_at.rest = $(wordlist 2,$(words $1),$1)
+_at.reverse = $(if $1,$(call _at.reverse,$(_at.rest))) $(firstword $1)
+
+at.dirlocal += at.subdirs
+at.dirlocal += at.depdirs
+
+_at.outdirs ?=
+_at.included_makefiles ?=
+
+include $(sort $(wildcard $(topsrcdir)/build-aux/Makefile.once.head/*.mk))
+
+endif # _at.NO_ONCE
+
+# This bit gets evaluated for each Makefile
+
+## Set outdir and srcdir (assumes that topoutdir and topsrcdir are
+## already set)
+outdir := $(call at.path,$(dir $(lastword $(filter-out %.mk,$(MAKEFILE_LIST)))))
+srcdir := $(call at.path,$(topsrcdir)/$(call _at.relto,$(topoutdir),$(outdir)))
+
+_at.included_makefiles := $(_at.included_makefiles) $(call at.path,$(outdir)/$(at.Makefile))
+
+$(foreach v,$(at.dirlocal),$(eval $v=))
+
+include $(sort $(wildcard $(topsrcdir)/build-aux/Makefile.each.head/*.mk))