ListCommitsByOid: add histogram for request size
We have some indications that there is a problem with the number of ListCommitsByOid calls made by gitlab-rails. https://gitlab.com/gitlab-com/gl-infra/production/issues/1403#note_249007796
This MR adds a histogram to give us insight into how ListCommitsByOid gets used: how many commits are being requested. Is ListCommitsByOid a glorified version of FindCommit? This MR would let us detect that.
Edited by GitLab Release Tools Bot