@@ -1,4 +1,6 @@
 /fuzz_corpora
+/target/
+/Cargo.lock
 /GIT-BUILD-DIR
 /GIT-BUILD-OPTIONS
 /GIT-CFLAGS

@@ -483,6 +483,14 @@ include shared.mak
 # Define LIBPCREDIR=/foo/bar if your PCRE header and library files are
 # in /foo/bar/include and /foo/bar/lib directories.
 #
+# == Optional Rust support ==
+#
+# Define WITH_RUST if you want to include features and subsystems written in
+# Rust into Git. For now, Rust is still an optional feature of the build
+# process. With Git 3.0 though, Rust will always be enabled.
+#
+# Building Rust code requires Cargo.
+#
 # == SHA-1 and SHA-256 defines ==
 #
 # === SHA-1 backend ===

@@ -683,6 +691,7 @@ OBJECTS =
 OTHER_PROGRAMS =
 PROGRAM_OBJS =
 PROGRAMS =
+RUST_SOURCES =
 EXCLUDED_PROGRAMS =
 SCRIPT_PERL =
 SCRIPT_PYTHON =

@@ -918,6 +927,11 @@ TEST_SHELL_PATH = $(SHELL_PATH)
 LIB_FILE = libgit.a
 XDIFF_LIB = xdiff/lib.a
 REFTABLE_LIB = reftable/libreftable.a
+ifdef DEBUG
+RUST_LIB = target/debug/libgit.a
+else
+RUST_LIB = target/release/libgit.a
+endif
 
 # xdiff and reftable libs may in turn depend on what is in libgit.a
 GITLIBS = common-main.o $(LIB_FILE) $(XDIFF_LIB) $(REFTABLE_LIB) $(LIB_FILE)

@@ -943,6 +957,15 @@ BASIC_LDFLAGS =
 ARFLAGS = rcs
 PTHREAD_CFLAGS =
 
+# Rust flags
+CARGO_ARGS =
+ifndef V
+CARGO_ARGS += --quiet
+endif
+ifndef DEBUG
+CARGO_ARGS += --release
+endif
+
 # For the 'sparse' target
 SPARSE_FLAGS ?= -std=gnu99 -D__STDC_NO_VLA__
 SP_EXTRA_FLAGS =

@@ -1475,6 +1498,8 @@ CLAR_TEST_OBJS += $(UNIT_TEST_DIR)/unit-test.o
 
 UNIT_TEST_OBJS += $(UNIT_TEST_DIR)/test-lib.o
 
+RUST_SOURCES += src/lib.rs
+
 GIT-VERSION-FILE: FORCE
 	@OLD=$$(cat $@ 2>/dev/null || :) && \
 	$(call version_gen,"$(shell pwd)",GIT-VERSION-FILE.in,$@) && \

@@ -1504,6 +1529,11 @@ endif
 ALL_CFLAGS = $(DEVELOPER_CFLAGS) $(CPPFLAGS) $(CFLAGS) $(CFLAGS_APPEND)
 ALL_LDFLAGS = $(LDFLAGS) $(LDFLAGS_APPEND)
 
+ifdef WITH_RUST
+BASIC_CFLAGS += -DWITH_RUST
+GITLIBS += $(RUST_LIB)
+endif
+
 ifdef SANITIZE
 SANITIZERS := $(foreach flag,$(subst $(comma),$(space),$(SANITIZE)),$(flag))
 BASIC_CFLAGS += -fsanitize=$(SANITIZE) -fno-sanitize-recover=$(SANITIZE)

@@ -2918,6 +2948,12 @@ scalar$X: scalar.o GIT-LDFLAGS $(GITLIBS)
 $(LIB_FILE): $(LIB_OBJS)
 	$(QUIET_AR)$(RM) $@ && $(AR) $(ARFLAGS) $@ $^
 
+$(RUST_LIB): Cargo.toml $(RUST_SOURCES)
+	$(QUIET_CARGO)cargo build $(CARGO_ARGS)
+
+.PHONY: rust
+rust: $(RUST_LIB)
+
 $(XDIFF_LIB): $(XDIFF_OBJS)
 	$(QUIET_AR)$(RM) $@ && $(AR) $(ARFLAGS) $@ $^
 

@@ -3768,6 +3804,7 @@ clean: profile-clean coverage-clean cocciclean
 	$(RM) $(FUZZ_PROGRAMS)
 	$(RM) $(SP_OBJ)
 	$(RM) $(HCC)
+	$(RM) -r Cargo.lock target/
 	$(RM) version-def.h
 	$(RM) -r $(dep_dirs) $(compdb_dir) compile_commands.json
 	$(RM) $(test_bindir_programs)

@@ -56,6 +56,7 @@ ifndef V
 	QUIET_MKDIR_P_PARENT  = @echo '   ' MKDIR -p $(@D);
 
 ## Used in "Makefile"
+	QUIET_CARGO    = @echo '   ' CARGO $@;
 	QUIET_CC       = @echo '   ' CC $@;
 	QUIET_AR       = @echo '   ' AR $@;
 	QUIET_LINK     = @echo '   ' LINK $@;