Add shell.execute

This functions the same as shell.run, but does not tokenise the
arguments. This allows us to pass command line arguments through to
another program without having to re-quote them.

Closes #417

src/main/resources/assets/computercraft/lua/rom/programs/monitor.lua

@@ -28,7 +28,7 @@ local monitor = peripheral.wrap(sName)
 local previousTerm = term.redirect(monitor)
 
 local co = coroutine.create(function()
-    shell.run(sProgram, table.unpack(tArgs, 3))
+    (shell.execute or shell.run)(sProgram, table.unpack(tArgs, 3))
 end)
 
 local function resume(...)

src/main/resources/assets/computercraft/lua/rom/programs/shell.lua

@@ -130,8 +130,25 @@ else
     bgColour = colours.black
 end
 
-local function run(_sCommand, ...)
-    local sPath = shell.resolveProgram(_sCommand)
+--- Run a program with the supplied arguments.
+--
+-- Unlike @{shell.run}, each argument is passed to the program verbatim. While
+-- `shell.run("echo", "b c")` runs `echo` with `b` and `c`,
+-- `shell.execute("echo", "b c")` runs `echo` with a single argument `b c`.
+--
+-- @tparam string command The program to execute.
+-- @tparam string ... Arguments to this program.
+-- @treturn boolean Whether the program exited successfully.
+-- @usage Run `paint my-image` from within your program:
+--
+--     shell.execute("paint", "my-image")
+function shell.execute(command, ...)
+    expect(1, command, "string")
+    for i = 1, select('#', ...) do
+        expect(i + 1, select(i, ...), "string")
+    end
+
+    local sPath = shell.resolveProgram(command)
     if sPath ~= nil then
         tProgramStack[#tProgramStack + 1] = sPath
         if multishell then
@@ -144,7 +161,7 @@ local function run(_sCommand, ...)
 
         local sDir = fs.getDir(sPath)
         local env = createShellEnv(sDir)
-        env.arg = { [0] = _sCommand, ... }
+        env.arg = { [0] = command, ... }
         local result = os.run(env, sPath, ...)
 
         tProgramStack[#tProgramStack] = nil
@@ -196,11 +213,12 @@ end
 -- @usage Run `paint my-image` from within your program:
 --
 --     shell.run("paint", "my-image")
+-- @see shell.execute Run a program directly without parsing the arguments.
 function shell.run(...)
     local tWords = tokenise(...)
     local sCommand = tWords[1]
     if sCommand then
-        return run(sCommand, table.unpack(tWords, 2))
+        return shell.execute(sCommand, table.unpack(tWords, 2))
     end
     return false
 end

src/test/resources/test-rom/data/dump-args.lua

@@ -0,0 +1 @@
+_G.__arg = _ENV.arg

src/test/resources/test-rom/spec/programs/shell_spec.lua

@@ -6,19 +6,25 @@ describe("The shell", function()
         end)
     end)
 
-    describe("shell.run", function()
-        it("sets the arguments", function()
-            local handle = fs.open("test-files/out.txt", "w")
-            handle.writeLine("_G.__arg = arg")
-            handle.close()
-
-            shell.run("/test-files/out.txt", "arg1", "arg2")
-            fs.delete("test-files/out.txt")
+    describe("shell.execute", function()
+        it("parses in arguments verbatim", function()
+            shell.execute("/test-rom/data/dump-args", "arg1", "arg 2")
 
             local args = _G.__arg
             _G.__arg = nil
 
-            expect(args):same { [0] = "/test-files/out.txt", "arg1", "arg2" }
+            expect(args):same { [0] = "/test-rom/data/dump-args", "arg1", "arg 2" }
+        end)
+    end)
+
+    describe("shell.run", function()
+        it("tokenises the arguments", function()
+            shell.run("/test-rom/data/dump-args", "arg1", "arg 2")
+
+            local args = _G.__arg
+            _G.__arg = nil
+
+            expect(args):same { [0] = "/test-rom/data/dump-args", "arg1", "arg", "2" }
         end)
     end)