From 47980db72ba4409439632c8f916eb75ab10ffe78 Mon Sep 17 00:00:00 2001
From: Joshua Nelson <jyn514@gmail.com>
Date: Fri, 1 Jan 2021 11:52:31 -0500
Subject: [PATCH] Choose an appropriate python version for x.py at runtime

- Default to python3 -> python -> python2
- Start as shell script and re-execute the program with the right python
  interpreter
---
 x.py | 16 +++++++++++++++-
 1 file changed, 15 insertions(+), 1 deletion(-)

diff --git a/x.py b/x.py
index 7973730ef177c..60cc589cd6388 100755
--- a/x.py
+++ b/x.py
@@ -1,4 +1,18 @@
-#!/usr/bin/env python
+# The beginning of this script is both valid shell and valid python, such that
+# the script starts with the shell and is reexecuted with the right python.
+# This works because shells only execute a line at a time.
+# Thanks to `./mach` from servo for the idea!
+''':' && {
+exists() { command -v "$1" >/dev/null 2>&1; }
+if exists python3; then
+    exec python3 "$0" "$@"
+elif exists python; then
+    exec python "$0" "$@"
+else
+    exec python2 "$0" "$@"
+fi
+}
+'''
 
 # This file is only a "symlink" to bootstrap.py, all logic should go there.