New get_user_input() function for consistent handling of user input.

The available answers are provided in a dictionary and the prompt is
generated from them.
Also, answers are higlighted if the terminal supports it.

osc/output/__init__.py

@@ -1,4 +1,5 @@
 from .key_value_table import KeyValueTable
+from .input import get_user_input
 from .tty import colorize
 from .widechar import wc_ljust
 from .widechar import wc_width

osc/output/input.py

@@ -0,0 +1,51 @@
+import sys
+import textwrap
+from typing import Dict
+from typing import Optional
+
+from .. import oscerr
+from .tty import colorize
+
+
+def get_user_input(question: str, answers: Dict[str, str], default_answer: Optional[str] = None) -> str:
+    """
+    Ask user a question and wait for reply.
+
+    :param question: The question. The text gets automatically dedented and stripped.
+    :param answers: A dictionary with answers. Keys are the expected replies and values are their descriptions.
+    :param default_answer: The default answer. Must be ``None`` or match an ``answers`` entry.
+    """
+
+    if default_answer and default_answer not in answers:
+        raise ValueError(f"Default answer doesn't match any answer: {default_answer}")
+
+    question = textwrap.dedent(question)
+    question = question.strip()
+
+    prompt = []
+    for key, value in answers.items():
+        value = f"{colorize(key, 'bold')}){value}"
+        prompt.append(value)
+
+    prompt_str = " / ".join(prompt)
+    if default_answer:
+        prompt_str += f" (default={colorize(default_answer, 'bold')})"
+    prompt_str += ": "
+
+    print(question, file=sys.stderr)
+
+    while True:
+        try:
+            reply = input(prompt_str)
+        except EOFError:
+            # interpret ctrl-d as user abort
+            raise oscerr.UserAbort()  # pylint: disable=raise-missing-from
+
+        if reply in answers:
+            return reply
+        if reply.strip() in answers:
+            return reply.strip()
+        if not reply.strip():
+            return default_answer
+
+        print(f"Invalid reply: {colorize(reply, 'bold,red')}", file=sys.stderr)