Update README on new env var

Closes #13

README.md

@@ -51,10 +51,17 @@ $your_image_viewer blah_g1.bmp
 using repl works via `scritcher repl scri_file.scri input_image.bmp`
 
 you type commands as you'd write the specific scritcher commands
-(`doc/README.md`), with three repl-specific ones:
+(`doc/README.md`), with four repl-specific ones (semicolons do not apply):
  - `push`, to push the last written command to the queue
  - `save`, to write the queue to the given `scri_file.scri` file
  - `list`, to print the current contents of the queue
+ - `quit`, to exit
 
-this allows for quicker iteration of commands, as you can type a command, tweak
-its arguments, and when satisfied, `push` it, and work on the next one, etc.
+After a non-REPL command, such as an effect, the program pointed by
+`SCRITCHER_RUNNER` will run as argument to the `runqs` command. By default,
+the program run will be `ristretto` (as it is my preffered image viewer,
+considering it was able to handle when some images went broke)
+
+this allows for quicker iteration of commands, as you can type a command, see
+the image changes as fast as possible, tweak its arguments,
+and when satisfied, `push` it, and work on the next command, etc.

src/main.zig

@@ -104,8 +104,8 @@ pub fn doRepl(allocator: *std.mem.Allocator, args_it: var) !void {
     var runqs_args = langs.ArgList.init(allocator);
     defer runqs_args.deinit();
 
-    // TODO change the runqs command to something given in an env var
-    try runqs_args.append("ristretto");
+    const wanted_runner: []const u8 = std.os.getenv("SCRITCHER_RUNNER") orelse "ristretto";
+    try runqs_args.append(wanted_runner);
 
     while (true) {
         lang.reset();
@@ -182,7 +182,7 @@ pub fn main() !void {
     // TODO print help
 
     _ = try (args_it.next(allocator) orelse @panic("expected exe name"));
-    const scri_path = try (args_it.next(allocator) orelse @panic("expected scri path"));
+    const scri_path = try (args_it.next(allocator) orelse @panic("expected scri path or 'repl'"));
 
     if (std.mem.eql(u8, scri_path, "repl")) {
         return try doRepl(allocator, &args_it);