Support for "+=" in service settings ("command" only)

This adds support for "+=" operator as a way to append to setting values
in service description files (instead of "=" which is currently used for
assignment). For the moment, it is implemented only for the "command"
setting.

This should be useful for user customisation of system services - the
user can override the system service description, but @include the
original, and then add extra arguments to the command line via "command
+= ...".

Support for additional commands, tests, and documentation will follow.

src/Makefile

@@ -10,7 +10,7 @@ ifeq ($(BUILD_SHUTDOWN),yes)
 endif
 
 dinit_objects = dinit.o load-service.o service.o proc-service.o baseproc-service.o control.o dinit-log.o \
-		dinit-main.o run-child-proc.o options-processing.o dinit-env.o
+		dinit-main.o run-child-proc.o options-processing.o dinit-env.o settings.o
 
 objects = $(dinit_objects) dinitctl.o dinitcheck.o shutdown.o dinit-monitor.o
 
@@ -23,11 +23,11 @@ all: dinit dinitctl dinitcheck dinit-monitor $(SHUTDOWN)
 dinit: $(dinit_objects)
 	$(CXX) -o dinit $(dinit_objects) $(ALL_LDFLAGS)
 
-dinitctl: dinitctl.o options-processing.o
-	$(CXX) -o dinitctl dinitctl.o options-processing.o $(ALL_LDFLAGS)
+dinitctl: dinitctl.o options-processing.o settings.o
+	$(CXX) -o dinitctl dinitctl.o options-processing.o settings.o $(ALL_LDFLAGS)
 
-dinitcheck: dinitcheck.o options-processing.o
-	$(CXX) -o dinitcheck dinitcheck.o options-processing.o $(ALL_LDFLAGS)
+dinitcheck: dinitcheck.o options-processing.o settings.o
+	$(CXX) -o dinitcheck dinitcheck.o options-processing.o settings.o $(ALL_LDFLAGS)
 
 dinit-monitor: dinit-monitor.o
 	$(CXX) -o dinit-monitor dinit-monitor.o $(ALL_LDFLAGS)

src/dinitcheck.cc

@@ -658,7 +658,7 @@ service_record *load_service(service_set_t &services, const std::string &name,
 
     try {
         process_service_file(name, input_stack,
-                [&](string &line, file_pos_ref input_pos, string &setting,
+                [&](string &line, file_pos_ref input_pos, string &setting, setting_op_t op,
                         string_iterator &i, string_iterator &end) -> void {
 
             auto process_dep_dir_n = [&](std::list<prelim_dep> &deplist, const std::string &waitsford,
@@ -671,7 +671,7 @@ service_record *load_service(service_set_t &services, const std::string &name,
             };
 
             try {
-                process_service_line(settings, name.c_str(), line, input_pos, setting, i, end,
+                process_service_line(settings, name.c_str(), line, input_pos, setting, op, i, end,
                         load_service_n, process_dep_dir_n);
             }
             catch (service_description_exc &exc) {

src/dinitctl.cc

@@ -1775,7 +1775,8 @@ static int enable_disable_service(int socknum, cpbuffer_t &rbuffer, service_dir_
     input_stack.push(service_file_path, std::move(service_file));
 
     try {
-        process_service_file(from, input_stack, [&](string &line, file_pos_ref fpr, string &setting,
+        process_service_file(from, input_stack, [&](string &line, file_pos_ref fpr,
+                string &setting, dinit_load::setting_op_t op,
                 dinit_load::string_iterator i, dinit_load::string_iterator end) -> void {
             if (setting == "waits-for" || setting == "depends-on" || setting == "depends-ms") {
                 string dname = dinit_load::read_setting_value(fpr, i, end);