Make z -i and z -I with no arguments be interactive.

In skywind3000/z.lua#122 there's a note that z.lua intentionally doesn't
support `z -i` being interactive to maintain consistency with how z.sh
behaves with `z -i`.  But z.sh doesn't have a `-i` option, so I'm not
sure what is the intent.

This commit makes `z -i` and `z -I` go interactive even with no args.

z.cmd

@@ -89,7 +89,9 @@ if /i "%1"=="--purge" (
 :check
 
 if /i "%1"=="" (
-	set "RunMode=-l"
+	if /i "%InterMode%"=="" (
+		set "RunMode=-l"
+	)
 )
 
 for /f "delims=" %%i in ('cd') do set "PWD=%%i"

z.lua

@@ -1612,21 +1612,23 @@ function z_cd(patterns)
 	if patterns == nil then
 		return nil
 	end
-	if #patterns == 0 then
-		return nil
-	end
-	local last = patterns[#patterns]
-	if last == '~' or last == '~/' then
-		return os.path.expand('~')
-	elseif windows and last == '~\\' then
-		return os.path.expand('~')
-	end
-	if os.path.isabs(last) and os.path.isdir(last) then
-		local size = #patterns
-		if size <= 1 then
-			return os.path.norm(last)
-		elseif last ~= '/' and last ~= '\\' then
-			return os.path.norm(last)
+	if Z_INTERACTIVE == 0 then
+		if #patterns == 0 then
+			return nil
+		end
+		local last = patterns[#patterns]
+		if last == '~' or last == '~/' then
+			return os.path.expand('~')
+		elseif windows and last == '~\\' then
+			return os.path.expand('~')
+		end
+		if os.path.isabs(last) and os.path.isdir(last) then
+			local size = #patterns
+			if size <= 1 then
+				return os.path.norm(last)
+			elseif last ~= '/' and last ~= '\\' then
+				return os.path.norm(last)
+			end
 		end
 	end
 	local M = z_match(patterns, Z_METHOD, Z_SUBDIR)
@@ -1971,7 +1973,7 @@ function main(argv)
 			end
 		elseif options['-'] then
 			path = cd_minus(args, options)
-		elseif #args == 0 then
+		elseif #args == 0 and Z_INTERACTIVE == 0 then
 			path = nil
 		else
 			path = z_cd(args)