touch(truncate=True) is a bad default

What happened:

I wanted to update the timestamp on 2000 objects, comprising of 5 TB of data on Google Cloud. So I ran

for obj in obj_list:
    fs.touch(obj)

What you expected to happen:

Consistent with my experience with the unix touch command, I assumed the default behavior would be to just update the modification time. Instead, I lost 5 TB of valuable data. This is my fault, for not reading the docstring

Signature: fs.touch(path, truncate=True, **kwargs)
Docstring:
Create empty file, or update timestamp

Parameters
----------
path: str
    file location
truncate: bool
    If True, always set file size to 0; if False, update timestamp and
    leave file unchanged, if backend allows this

However, I would argue that this is a very bad default value for truncate. Why deviate from the standard unix behavior? I can't be the first user to make this mistake...

The issue identifies fs.touch(path, truncate=True, **kwargs) and its docstring as the relevant entry point; start there and inspect how the default is documented and exercised. Decide whether the default should match Unix touch semantics, then update the behavior and documentation so the default preserves existing data while an explicit truncation option remains available.