Add a new target help_vars

This target can display all variables that can be overridden

Arduino.mk

@@ -1184,7 +1184,7 @@ size:	$(TARGET_HEX)
 		$(call avr_size,$(TARGET_ELF),$(TARGET_HEX))
 
 show_boards:
-		@cat $(BOARDS_TXT) | grep -E "^[[:alnum:]]" | cut -d . -f 1 | uniq
+		@$(CAT) $(BOARDS_TXT) | grep -E "^[[:alnum:]]" | cut -d . -f 1 | uniq
 
 monitor:
 		$(MONITOR_CMD) $(call get_monitor_port) $(MONITOR_BAUDRATE)
@@ -1208,6 +1208,9 @@ generate_assembly: $(OBJDIR)/$(TARGET).s
 generated_assembly: generate_assembly
 		@$(ECHO) "\"generated_assembly\" target is deprecated. Use \"generate_assembly\" target instead"
 
+help_vars:
+		@$(CAT) $(ARDMK_DIR)/arduino-mk-vars.md
+
 help:
 		@$(ECHO) "\nAvailable targets:\n\
   make                  - no upload\n\
@@ -1229,6 +1232,7 @@ help:
   make raw_eeprom       - upload the eep file without first resetting\n\
   make burn_bootloader  - burn bootloader and fuses\n\
   make set_fuses        - set fuses without burning bootloader\n\
+  make help_vars        - print all variables that can be overridden\n\
   make help             - show this help\n\
 "
 	@$(ECHO) "Please refer to $(ARDMK_DIR)/Arduino.mk for more details.\n"

HISTORY.md

@@ -7,6 +7,7 @@ I tried to give credit whenever possible. If I have missed anyone, kindly add it
 ### 1.3.1 (2014-02-01)
 - Fix: BUNDLED_AVR_TOOLS_DIR is now set properly when using only arduino-core and not the whole arduino package. (https://github.com/sej7278)
 - New: Document all variables that can be overridden. (https://github.com/sej7278)
+- New: Add a new `help_vars` target to display information about variables that can be overridden.
 
 ### 1.3.0 (2014-01-29)
 - Fix: Use more reliable serial device naming in Windows. Fix issue #139 and #155 (https://github.com/peplin)