--- a/README.md	Mon Oct 24 00:41:04 2016 +0800
+++ b/README.md	Mon Oct 24 14:05:51 2016 +0800
@@ -43,5 +43,4 @@
 
 - Better docs
 - Maybe use something better than lpc
-- Handle cases when command needs input, but user provided nil
 - ??????

--- a/hglib.lua	Mon Oct 24 00:41:04 2016 +0800
+++ b/hglib.lua	Mon Oct 24 14:05:51 2016 +0800
@@ -157,6 +157,7 @@
 	local o = ''
 	local e = ''
 	local d = ''
+	input = input or ''
 	local function write_input(length)
 		write_block(self.wh, input:sub(1, length))
 		self.wh:flush()
@@ -175,9 +176,9 @@
 			e = e .. message
 		elseif channel == 'd' then
 			d = d .. message
-		elseif channel == 'I' and input ~= nil then
+		elseif channel == 'I' then
 			write_input(message)
-		elseif channel == 'L' and input ~= nil then
+		elseif channel == 'L' then
 			write_input(math.min(input:find('\n') or message, message))
 		elseif channel:lower() ~= channel then
 			e = e .. '\nhglib: unexpected data on required channel "' .. channel .. '"'

--- a/spec/hglib_spec.lua	Mon Oct 24 00:41:04 2016 +0800
+++ b/spec/hglib_spec.lua	Mon Oct 24 14:05:51 2016 +0800
@@ -92,6 +92,13 @@
 			assert.are_equal(0, code)
 		end
 		do
+			local code, o, e, d = client:runcommand({'-R', 'testrepo', 'import', '-'})
+			assert.is_not_nil(o:find('applying patch from stdin'))
+			assert.is_not_nil(e:find('abort: stdin: no diffs found'))
+			assert.are_equal('', d)
+			assert.are_equal(255, code)
+		end
+		do
 			local pf = assert(io.open('spec/data/foo.patch', 'rb'))
 			local patch = pf:read('*all')
 			pf:close()