Have naked $ make list all tasks

CONTRIBUTING.md

@@ -59,8 +59,10 @@ $ git checkout -b my_topical_branch
 
 #### Setup
 
-The [Makefile](https://github.com/httpie/httpie/blob/master/Makefile) contains a bunch of tasks to get you started. Just run
-the following command, which:
+The [Makefile](https://github.com/httpie/httpie/blob/master/Makefile) contains a bunch of tasks to get you started.
+You can run `$ make` to see all the available tasks.
+
+To get started, run the command below, which:
 
 - Creates an isolated Python virtual environment inside `./venv`
   (via the standard library [venv](https://docs.python.org/3/library/venv.html) tool);
@@ -70,7 +72,7 @@ the following command, which:
 - and runs tests (It is the same as running `make install test`).
 
 ```bash
-$ make
+$ make all
 ```
 
 #### Python virtual environment

Makefile

@@ -22,6 +22,26 @@ VENV_PYTHON=$(VENV_BIN)/python
 export PATH := $(VENV_BIN):$(PATH)
 
 
+
+default: list-tasks
+
+
+###############################################################################
+# Default task to get a list of tasks when `make' is run without args.
+# <https://stackoverflow.com/questions/4219255>
+###############################################################################
+
+list-tasks:
+	@echo Available tasks:
+	@echo ----------------
+	@$(MAKE) -pRrq -f $(lastword $(MAKEFILE_LIST)) : 2>/dev/null | awk -v RS= -F: '/^# File/,/^# Finished Make data base/ {if ($$1 !~ "^[#.]") {print $$1}}' | sort | egrep -v -e '^[^[:alnum:]]' -e '^$@$$'
+	@echo
+
+
+###############################################################################
+# Installation
+###############################################################################
+
 all: uninstall-httpie install test