This improves diff hunk name detection. Needed for checkpatch to
correctly detect if patched code belongs to a function.

NO_DOC=git
NO_TEST=git
NO_CHANGELOG=git

We often commit snap/xlog files for tests. A snap/xlog file is binary,
but it contains a plain text header and, as a result, may be identified
as a text file by git, which would enable checkpatch checks for it.
Apparently, we don't need to check these files so let's force git to
identify them as binary.

NO_DOC=git
NO_TEST=git
NO_CHANGELOG=git