add vwc support. fix a tiny unfound bug(without harm).

.gitignore

@@ -3,3 +3,4 @@ template/*
 !template/Vivadofile
 !template/*.xdc
 
+*.bit

README.md

@@ -10,6 +10,8 @@
 
 - Burn auto saved built binary at anytime and any machine.
 
+- Built-in support to an extremely simple constraint file format: `.vwc`.
+
 - Full vivado GUI support.
 
 - Support every hardware supported by vivado. 
@@ -68,6 +70,6 @@ vivadow gui
 
 ## Notice
 
-This is a bash script, so it can be easily injected. Never trust Vivadofile uploaded by others!
+This is a bash script, so it can be easily injected. `Vivadofile` and `.vwc` constraint will be directly `source`d. **Never** trust Vivadofile uploaded by others!
 
 If you give a wrong top\_module name, *silly vivado* will accept it, and generate bitstream for a **randomly-taken** module(with long time spent), then report error.

example/Vivadofile

@@ -1,13 +1,37 @@
-# Optional options
-# vivado_exec="/home/recolic/extraDisk/xilinx/Vivado/2018.1/bin/vivado"
-thread_num=4
-
+#
 # Required options
+#
+
+# You may use SystemVerilog, Verilog, or VHDL files as sources.
+# sources=(test_main.sv lib/* ./mod?.v)
 sources=(test_main.sv lib/* ./mod?.v)
+
+# The directory where generated bitstream is put
 bit_dir=./build
 
+# All of your top_modules and its constraint files.
+# top_modules=(
+#     "test_main:constraint/test_main.xdc"
+#     "mod1:constraint/mod1.vwc"
+# )
 top_modules=(
     "test_main:constraint/test_main.xdc"
-    "mod1:constraint/mod1.xdc"
+    "mod1:constraint/mod1.vwc"
 )
+
+# Your default top_module. Maybe override by commandline option.
+# top_module=test_main
 top_module=test_main
+
+# Name of your board in vivado. HUST uses 'xc7a100tcsg324-1' by default.
+board="xc7a100tcsg324-1"
+
+#
+# Optional options
+#
+
+# Path to vivado executable. It will override environment variable `vivado_exec`
+# vivado_exec="/path/to/vivado"
+
+# It's recommanded to set thread_num to cores of your CPU.
+thread_num=4

example/constraint/mod1.vwc

@@ -0,0 +1,2 @@
+vwc_port P4 i
+vwc_port T8 j

template/Vivadofile

@@ -12,7 +12,7 @@ bit_dir=./build
 # All of your top_modules and its constraint files.
 # top_modules=(
 #     "test_main:constraint/test_main.xdc"
-#     "mod1:constraint/mod1.xdc"
+#     "mod1:constraint/mod1.vwc"
 # )
 top_modules=(