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.