pants --changed-since treats any changes to a BUILD file as affecting all targets in that BUILD file

[mattalbr]

Describe the bug

$ git checkout dev
$ pants --changed-since=dev list
<empty, obviously>

then I modify whitespace in my file backend/BUILD (literally just remove an empty line)

pants --changed-since=dev list
<every target in backend/BUILD>

Pants version
2.31.0

OS
Docker on MacOS

Additional info
Obviously parsing the changes to the BUILD file is much harder than just looking at file-level changes, but IMO it's a bug to treat unaffected targets in the same BUILD file as affected.