install target custom

Makefile

@@ -9,6 +9,8 @@
 #                           the command line, e.g. make CC=clang CFLAGS=-O1
 #   .PHONY           not POSIX - see the FORCE target at the bottom
 #   target-specific variables, ifeq, wildcard, -include, ... all non-POSIX
+#   $(patsubst ...)  not POSIX - so the install directory is resolved by the
+#                           recipe shell, see INSTALL_DIR below
 #
 # Rule syntax used here: recipe lines start with a TAB, macros are written
 # $(NAME) (POSIX also accepts ${NAME}), and the only automatic macro used is
@@ -82,18 +84,68 @@ static-deps: FORCE
 static-deps-force: FORCE
 	FORCE=1 sh ./mkstaticdeps.sh
 
-# Install paths. DESTDIR and PREFIX may be set on the command line:
-# make install DESTDIR=/tmp/pkg PREFIX=/usr
+# Install paths. Every one of these can be set on the command line, so the
+# install target takes any location you name:
+#
+#   make install                          # $(DESTDIR)$(BINDIR) = /usr/local/bin
+#   make install PREFIX=$HOME/.local      # ~/.local/bin
+#   make install BINDIR=/opt/solo/bin     # an explicit directory
+#   make install DIR=/opt/solo/bin        # the same, spelled in one macro
+#   make install DIR=~/.local/bin         # a leading ~ is expanded, see below
+#   make install DIR=/usr/bin INSTALL="install -C"
+#   make install DESTDIR=/tmp/pkg DIR=/usr/bin   # staged, for packaging
+#
+# DIR wins over BINDIR when both are given; DESTDIR is prepended either way, so
+# "make install DESTDIR=/tmp/pkg DIR=/usr/bin" stages into /tmp/pkg/usr/bin.
+DESTDIR =
 PREFIX = /usr/local
 BINDIR = $(PREFIX)/bin
+DIR =
 INSTALL = install
 
-install: solo FORCE
-	$(INSTALL) -d $(DESTDIR)$(BINDIR)
-	$(INSTALL) -m 755 solo $(DESTDIR)$(BINDIR)/solo
+# The installation directory, as a shell snippet that prints it on stdout.
+#
+# POSIX make has no string functions, so "DIR if set, else BINDIR" and the
+# leading ~ are handled by the recipe shell instead of by the makefile. Both
+# install and uninstall use this one snippet, so they always agree on the path.
+# $$(...) survives expansion of the macro and reaches the shell as $(...).
+INSTALL_DIR = d="$(DIR)"; \
+	test -n "$$d" || d="$(BINDIR)"; \
+	case "$$d" in \
+		'~') d="$$HOME";; \
+		'~/'*) d="$$HOME/$$(printf '%s' "$$d" | cut -c3-)";; \
+	esac; \
+	printf '%s%s\n' "$(DESTDIR)" "$$d"
 
+# Install solo, and solo-static too when it has been built. Prints the location
+# it used, so a script can see where the binaries went.
+install: solo FORCE
+	@dir=$$($(INSTALL_DIR)); \
+	echo "installing into $$dir"; \
+	$(INSTALL) -d "$$dir"; \
+	$(INSTALL) -m 755 solo "$$dir/solo"; \
+	if test -f solo-static; then \
+		$(INSTALL) -m 755 solo-static "$$dir/solo-static"; \
+	fi
+
+# Install the static binary only; fails if it has not been built yet.
+install-static: static FORCE
+	@dir=$$($(INSTALL_DIR)); \
+	echo "installing solo-static into $$dir"; \
+	$(INSTALL) -d "$$dir"; \
+	$(INSTALL) -m 755 solo-static "$$dir/solo-static"
+
+# Prints the installation directory that install would use, and nothing else.
+installdir: FORCE
+	@dir=$$($(INSTALL_DIR)); echo "$$dir"
+
+# Removes the binaries from the location resolved the same way, so
+# "make install DIR=~/.local/bin" is undone by
+# "make uninstall DIR=~/.local/bin".
 uninstall: FORCE
-	rm -f $(DESTDIR)$(BINDIR)/solo $(DESTDIR)$(BINDIR)/solo-static
+	@dir=$$($(INSTALL_DIR)); \
+	echo "removing from $$dir"; \
+	rm -f "$$dir/solo" "$$dir/solo-static"
 
 clean: FORCE
 	rm -f solo solo-static