Sync script: handle multi commit merges

[tmshort]

Fix the sync script to handle commits in a single merge.
The sorting doesn't work as the commit time is all the same, and the next sortable field is the headline.
The commit time is the same, but the authorship time for each commit might be different or out of order.
Add an ordinal to the list of commits from each branch. This is used to sort commits (in original order) with the same commit time.

This is for the bash-based sync scripts.

[tmshort]

This modifies no OLM code; so everything ought to pass.

[tmshort]

/retest

[grokspawn]

/label docs-approved
/label px-approved
/label qe-approved

downstream-only sync infrastructure changes only

[openshift-ci]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: grokspawn, tmshort

The full list of commands accepted by this bot can be found here.

The pull request process is described here

Needs approval from an approver in each of these files:

• DOWNSTREAM_OWNERS [grokspawn,tmshort]

Approvers can indicate their approval by writing /approve in a comment
Approvers can cancel approval by writing /approve cancel in a comment

[openshift-ci-robot]

/retest-required

Remaining retests: 0 against base HEAD 586ee40 and 2 for PR HEAD 0b8b027 in total

[openshift-ci]

@tmshort: all tests passed!

Full PR test history. Your PR dashboard.

Instructions for interacting with me using PR comments are available here. If you have questions or suggestions related to my behavior, please file an issue against the kubernetes/test-infra repository. I understand the commands that are listed here.