Reduce Gitaly calls in PostReceivesh-optimize-commit-deltas-post-receive

This commit reduces I/O load and memory utilization during PostReceive
for the common case when no project hooks or services are set up.

We saw a Gitaly N+1 issue in `CommitDelta` when many tags or branches
are pushed. We can reduce this overhead in the common case because we
observe that most new projects do not have any Web hooks or services,
especially when they are first created. Previously, `BaseHooksService`
unconditionally iterated through the last 20 commits of each ref to
build the `push_data` structure. The `push_data` structured was used in
numerous places:

1. Building the push payload in `EventCreateService`
2. Creating a CI pipeline
3. Executing project Web or system hooks
4. Executing project services
5. As the return value of `BaseHooksService#execute`
6. `BranchHooksService#invalidated_file_types`

We only need to generate the full `push_data` for items 3, 4, and 6.

Item 1: `EventCreateService` only needs the last commit and doesn't
actually need the commit deltas.

Item 2: In addition, `Ci::CreatePipelineService` only needed a subset of
the parameters.

Item 5: The return value of `BaseHooksService#execute` also wasn't being
used anywhere.

Item 6: This is only used when pushing to the default branch, so if
many tags are pushed we can save significant I/O here.

Closes https://gitlab.com/gitlab-org/gitlab-ce/issues/65878

Fic

1 files changed, 5 insertions, 0 deletions

diff --git a/changelogs/unreleased/sh-optimize-commit-deltas-post-receive.yml b/changelogs/unreleased/sh-optimize-commit-deltas-post-receive.yml
new file mode 100644
index 00000000000..cd63b9bf425
--- /dev/null
+++ b/changelogs/unreleased/sh-optimize-commit-deltas-post-receive.yml
@@ -0,0 +1,5 @@
+---
+title: Reduce Gitaly calls in PostReceive
+merge_request: 31741
+author:
+type: performance