ci: fix clang-tidy

[derekargueta]

clang-tidy is currently yielding:

...
Running clang-tidy-diff against master branch...
From https://github.com/envoyproxy/envoy
 * branch            master     -> FETCH_HEAD
fatal: ambiguous argument 'master..HEAD': unknown revision or path not in the working tree.
Use '--' to separate paths from revisions, like this:
'git <command> [<revision>...] -- [<file>...]'
No relevant changes found.

on all PRs. This reverts a small part of #8965 to go back to using the base commit (the commit from which the PR was split off from) for git diff.

Signed-off-by: Derek Argueta dereka@pinterest.com

[SaveTheRbtz]

How about set -o pipefail at the top, so issues like that could be caught earlier?

[derekargueta]

@SaveTheRbtz nice catch, I was just trying to figure out why the git fatal error passed CI. Sadly not the first time I've been bitten by a piped failure >.< will add

[derekargueta]

looks better

Running clang-tidy-diff against master branch...
From https://github.com/envoyproxy/envoy
 * branch            master     -> FETCH_HEAD
No relevant changes found.
##[section]Finishing: Run CI script

[zuercher]

(Filed #9145 for the macOS test flake.)

[lizan]

The reason to use SYSTEM_PULLREQUEST_TARGETBRANCH is it will generate large diff for PR agains release branch and take forever.

Also, AZP run's on HEAD at GH pull request merge commit (i.e. refs/pull/9140/merge), so the merge-base will just be HEAD, so this generates no diff.

[derekargueta]

I see, so the issue isn't with SYSTEM_PULLREQUEST_TARGETBRANCH but HEAD. Sounds like the correct fix here would be to replace HEAD with SYSTEM_PULLREQUEST_SOURCEBRANCH ?

[lizan]

actually, I think just git diff "${SYSTEM_PULLREQUEST_TARGETBRANCH}" will work, without ..HEAD?

[lizan]

Suggested change

	git diff "${SYSTEM_PULLREQUEST_TARGETBRANCH}" | filter_excludes | \
	git diff "remotes/origin/${SYSTEM_PULLREQUEST_TARGETBRANCH}" | filter_excludes | \

seems Azp checkout is slightly different and this should work.

[lizan]

delete this line?

[lizan]

I think this will work, thanks.

[lizan]

Thanks!