RFR: 1452: Can never notify on first commit

[Zhao Song]

I changed the logic when there is no notify history.

Originally, on the first commit of a new repo, the bot would find no notify history, so it will make the first commit as an initial state and it will not make any notification.

Now, on the first commit of a new repo, the bot would find no notify history too, but it will make the initial git hash as the initial state of the repo, so it will treat the first commit as an 'update' operation and will make notifications.

-------------

Commit messages:
 - Will nofity on first commit

Changes: https://git.openjdk.org/skara/pull/1385/files
 Webrev: https://webrevs.openjdk.org/?repo=skara&pr=1385&range=00
  Issue: https://bugs.openjdk.org/browse/SKARA-1452
  Stats: 190 lines in 4 files changed: 126 ins; 5 del; 59 mod
  Patch: https://git.openjdk.org/skara/pull/1385.diff
  Fetch: git fetch https://git.openjdk.org/skara pull/1385/head:pull/1385

PR: https://git.openjdk.org/skara/pull/1385