commit a03d233df10a418dc162cbdc4e5b09e704996377
author Edwin Kempin <ekempin@google.com> Tue Mar 16 15:55:41 2021 +0100
committer Edwin Kempin <ekempin@google.com> Wed Mar 17 13:56:44 2021 +0100
tree 433046fdd122646a67a6a3ea23d9a7b5589b2d62
parent 1d1757274ab465ac79553ced94fb82a55fbaf9cf

CodeOwnerApprovalCheck: Skip the file path when looking up OWNERS files

When checking code owner approvals we iterate over all files that are
touched in the change and lookup the OWNERS files that are relevant for
them. For each file we start at the file path and then iterate up the
parent folders to look for OWNERS files. E.g. for file
"/foo/bar/baz.md" we check the following OWNERS files:
1. /foo/bar/baz.md/OWNERS
2. /foo/bar/OWNERS
3. /foo/OWNERS
4. /OWNERS

If we know that the given path is a file path, as in
CodeOwnerApprovalCheck, we can skip the first lookup as we know that
this OWNERS file will never exist.

The lower layers (CodeOwnerConfigHierarchy) accept arbitrary paths (file
paths and folder paths). Hence they must continue to check for the
"<path>/OWNERS" file.

Skipping this lookup in CodeOwnersApprovalCheck may look like an
optimization that is not worth doing, but we saw such lookups of
non-existing OWNERS files take up to 10ms, which sums up if you have
changes that touch 1000s of files.

Signed-off-by: Edwin Kempin <ekempin@google.com>
Change-Id: I9be58eb55183ef9177ae0c12b85691b5a26a7abd