These errors are mostly fixed by either adding blank lines or single
spaces for Sphinx documentation key words.

The commit solely includes documentation changes, no functional
changes.

This reverts commit a7c5d88.

`flake8` seems to dislike the formatting of black.

That way people who use it won't be deterred, while it unifies style
everywhere.

This commit adds the `strip_newline` flag to the `Git.execute` method.
When this flag is set to `True`, it will trim the trailing `\n`. The
default value is `True` for backward compatibility. Setting it to
`False` is helpful for, e.g., the `git show` output, especially with the binary
file, as the missing `\n` may invalidate the file.

To create a window application with pyinstaller, all suprocess input and output streams must be assigned and must not be None.
https://stackoverflow.com/a/51706087/7076612

…let tests use it

General fixes for next release

Fixes #1334