Now fails if any commands fail. I noticed that on the buildbot, the
arguments to this script can be incorrect (somehow?) which can result in
no lint checks happening but the buildbot still passing.
Instead of applying PRs as patches and leaving them as staged changes,
the lint builder now checks out the PR branch, so the lint script
must be able to call git diff with more than just --cached.
(The buildbot will call it with "master...".)
It turns out that last fix was only partial, and it didn't fix the
issue completely as paths were fixed, but staged changes were not
in the list. This should fix it for real, this time. Sorry about that…
(git diff needs --cached to include staged changes, unlike git status.)
git diff --name-only already took care of only returning the name, so
the awk is unneeded and makes it return only empty file names.
Facepalm, I know. Sorry for this oversight.
(Also fixes something that lint didn't catch because of this)
