build: Replace `make config` with a `./configure` script

This lets us do more traditional out-of-tree builds like

    $ ../path/to/bfs/configure
    $ make

The .mk files are moved from ./config to ./build, mostly so that
./configure will auto-complete easily.

1 files changed, 133 insertions, 0 deletions

diff --git a/build/prelude.mk b/build/prelude.mk
new file mode 100644
index 0000000..b235fa9
--- /dev/null
+++ b/build/prelude.mk
@@ -0,0 +1,133 @@
+# Copyright © Tavian Barnes <tavianator@tavianator.com>
+# SPDX-License-Identifier: 0BSD
+
+# Common makefile utilities.  Compatible with both GNU make and most BSD makes.
+
+# BSD make will chdir into ${.OBJDIR} by default, unless we tell it not to
+.OBJDIR: .
+
+# We don't use any suffix rules
+.SUFFIXES:
+
+# GNU make has $^ for the full list of targets, while BSD make has $> and the
+# long-form ${.ALLSRC}.  We could write $^ $> to get them both, but that would
+# break if one of them implemented support for the other.  So instead, bring
+# BSD's ${.ALLSRC} to GNU.
+.ALLSRC ?= $^
+
+# Installation paths
+DESTDIR ?=
+PREFIX ?= /usr
+MANDIR ?= ${PREFIX}/share/man
+
+# Configurable executables
+CC ?= cc
+INSTALL ?= install
+MKDIR ?= mkdir -p
+PKG_CONFIG ?= pkg-config
+RM ?= rm -f
+
+# GNU and BSD make have incompatible syntax for conditionals, but we can do a
+# lot with just nested variable expansion.  We use "y" as the canonical
+# truthy value, and "" (the empty string) as the canonical falsey value.
+#
+# To normalize a boolean, use ${TRUTHY,${VAR}}, which expands like this:
+#
+#     VAR=y      ${TRUTHY,${VAR}} => ${TRUTHY,y}     => y
+#     VAR=1      ${TRUTHY,${VAR}} => ${TRUTHY,1}     => y
+#     VAR=n      ${TRUTHY,${VAR}} => ${TRUTHY,n}     =>   [empty]
+#     VAR=other  ${TRUTHY,${VAR}} => ${TRUTHY,other} =>   [empty]
+#     VAR=       ${TRUTHY,${VAR}} => ${TRUTHY,}      =>   [emtpy]
+#
+# Inspired by https://github.com/wahern/autoguess
+TRUTHY,y := y
+TRUTHY,1 := y
+
+# Boolean operators are also implemented with nested expansion
+NOT,  := y
+
+# Normalize ${V} to either "y" or ""
+IS_V := ${TRUTHY,${V}}
+
+# Suppress output unless V=1
+Q, := @
+Q  := ${Q,${IS_V}}
+
+# Show full commands with `make V=1`, otherwise short summaries
+MSG = @msg() { \
+          MSG="$$1"; \
+          shift; \
+          test "${IS_V}" || printf '%s\n' "$$MSG"; \
+          test "$${1:-}" || return 0; \
+          test "${IS_V}" && printf '%s\n' "$$*"; \
+          "$$@"; \
+      }; \
+      msg
+
+# Maximum width of a short message, to align the ✔/✘
+MSG_WIDTH := 30
+
+# cat a file if V=1
+VCAT,y := @cat
+VCAT,  := @:
+VCAT   := ${VCAT,${IS_V}}
+
+# All external dependencies
+ALL_PKGS := \
+    libacl \
+    libcap \
+    libselinux \
+    liburing \
+    oniguruma
+
+# List all object files here, as they're needed by both `./configure` and `make`
+
+# All object files except the entry point
+LIBBFS := \
+    obj/src/alloc.o \
+    obj/src/bar.o \
+    obj/src/bfstd.o \
+    obj/src/bftw.o \
+    obj/src/color.o \
+    obj/src/ctx.o \
+    obj/src/diag.o \
+    obj/src/dir.o \
+    obj/src/dstring.o \
+    obj/src/eval.o \
+    obj/src/exec.o \
+    obj/src/expr.o \
+    obj/src/fsade.o \
+    obj/src/ioq.o \
+    obj/src/mtab.o \
+    obj/src/opt.o \
+    obj/src/parse.o \
+    obj/src/printf.o \
+    obj/src/pwcache.o \
+    obj/src/stat.o \
+    obj/src/thread.o \
+    obj/src/trie.o \
+    obj/src/typo.o \
+    obj/src/xregex.o \
+    obj/src/xspawn.o \
+    obj/src/xtime.o \
+    obj/gen/version.o
+
+# Unit test objects
+UNIT_OBJS := \
+    obj/tests/alloc.o \
+    obj/tests/bfstd.o \
+    obj/tests/bit.o \
+    obj/tests/ioq.o \
+    obj/tests/main.o \
+    obj/tests/trie.o \
+    obj/tests/xspawn.o \
+    obj/tests/xtime.o
+
+# All object files
+OBJS := \
+    obj/src/main.o \
+    obj/tests/mksock.o \
+    obj/tests/xspawnee.o \
+    obj/tests/xtouch.o \
+    ${LIBBFS} \
+    ${UNIT_OBJS}