1 files changed, 49 insertions, 0 deletions
diff --git a/build-aux/Makefile.head.mk b/build-aux/Makefile.head.mk
new file mode 100644
index 0000000000..e4ae329a8f
--- /dev/null
+++ b/build-aux/Makefile.head.mk
@@ -0,0 +1,49 @@
+# 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 ($(_am_NO_ONCE),)
+
+_am = am_
+
+_am_noslash = $(patsubst %/.,%,$(patsubst %/,%,$1))
+# These are all $(call _am_func,parent,child)
+#_am_relto = $(if $2,$(shell realpath -sm --relative-to='$1' $2))
+_am_is_subdir = $(filter $(abspath $1)/%,$(abspath $2)/.)
+_am_relto_helper = $(if $(call _am_is_subdir,$1,$2),$(patsubst $1/%,%,$(addsuffix /.,$2)),$(addprefix ../,$(call _am_relto_helper,$(patsubst %/,%,$(dir $1)),$2)))
+_am_relto = $(call _am_noslash,$(call _am_relto_helper,$(call _am_noslash,$(abspath $1)),$(call _am_noslash,$(abspath $2))))
+# Note that _am_is_subdir says that a directory is a subdirectory of
+# itself.
+am_path = $(foreach p,$1,$(call _am_relto,.,$p))
+
+$(_am)dirlocal += $(_am)subdirs
+$(_am)dirlocal += $(_am)depdirs
+
+include $(topsrcdir)/common.once.head.mk
+
+endif # _am_NO_ONCE
+
+# This bit gets evaluated for each Makefile
+
+## Set outdir and srcdir (assumes that topoutdir and topsrcdir are
+## already set)
+outdir := $(call am_path,$(dir $(lastword $(filter-out %.mk,$(MAKEFILE_LIST)))))
+srcdir := $(call am_path,$(topsrcdir)/$(call _am_relto,$(topoutdir),$(outdir)))
+
+_am_included_makefiles := $(_am_included_makefiles) $(call am_path,$(outdir)/Makefile)
+
+$(foreach v,$($(_am)dirlocal),$(eval $v=))
+
+include $(topsrcdir)/common.each.head.mk