WIP Add support for Sage

(language_info is missing in sample notebook)

docs/languages.md

@@ -21,6 +21,7 @@ Jupytext works with notebooks in any of the following languages:
 - R
 - Robot Framework
 - Rust/Evxcr
+- Sage
 - Scala
 - Scheme
 - Script of Script

jupytext/languages.py

@@ -57,6 +57,7 @@
     ".sos": {"language": "sos", "comment": "#"},
     ".java": {"language": "java", "comment": "//"},
     ".groovy": {"language": "groovy", "comment": "//"},
+    ".sage": {"language": "sage", "comment": "#"},
 }
 
 _COMMENT_CHARS = [

tests/notebooks/ipynb_sage/sage_print_hello.ipynb

@@ -0,0 +1,22 @@
+{
+ "cells": [
+  {
+   "cell_type": "code",
+   "execution_count": null,
+   "metadata": {},
+   "outputs": [],
+   "source": [
+    "print(\"Hello world\")"
+   ]
+  }
+ ],
+ "metadata": {
+  "kernelspec": {
+   "display_name": "SageMath 9.2",
+   "language": "sage",
+   "name": "sagemath"
+  }
+ },
+ "nbformat": 4,
+ "nbformat_minor": 2
+}