What does "1 line adds whitespace errors" mean when applying a patch?
I'm editing some markdown files of a cloned remote repository, and wanted to test creating and applying patches from one branch to another. However, every time I make any change at all, I get the following message during git apply:
0001-b.patch:16: trailing whitespace.
warning: 1 line adds whitespace errors.
(This is happening on my Mac, and I don't know where the original code was created.)
What does the warning message mean, and do I need to care?
Answer
You don't need to care.
The warning enacts a standard of cleanliness of text files in regard to whitespace, the kind of thing that many programmers tend to care about. As the manual explains:
What are considered whitespace errors is controlled by core.whitespace configuration. By default, trailing whitespaces (including lines that solely consist of whitespaces) and a space character that is immediately followed by a tab character inside the initial indent of the line are considered whitespace errors.
By default, the command outputs warning messages but applies the patch.
So, the "error" means that the change introduces a trailing whitespace, a whitespace-only line, or a space that precedes a tab. Other than that fact, there is nothing erroneous about the change, and it will apply cleanly and correctly. In other words, if you don't care about the "incorrect" whitespace, feel free to ignore the warning or turn it off with git config apply.whitespace nowarn.