What does $.changes[0].toHash represent in a Bitbucket webhook when the event is a tag added?

Question

Our Bitbucker server is configured to invoke webhooks (received by Jenkins) on push events, which include branch updates, and tags added. The HTTP POST content included in this webhook is a JSON describing the event. The event payloads are described here: https://confluence.atlassian.com/bitbucketserver076/event-payload-1026535078.html

(I'll use "$" to refer to the root of the received JSON)

When I perform a git push origin {my_branch}, the JSON included in the webhook gives values for $.changes[0].fromHash and $.changes[0].toHash that I can correlate to my git log.
E.g., if the received JSON is:

{  
  "eventKey":"repo:refs_changed",
  "date":"2017-09-19T09:45:32+1000",
  "actor":{ ...  },
  "repository":{  ...  },
  "changes":[  
    {  
      "ref":{  
        "id":"refs/heads/master",
        "displayId":"master",
        "type":"BRANCH"
      },
      "refId":"refs/heads/master",
      "fromHash":"ecddabb624f6f5ba43816f5926e580a5f680a932",
      "toHash":"178864a7d521b6f5e720b386b2c2b0ef8563e0dc",
      "type":"UPDATE"
    }
  ]
}

...then I'd be able to see {fromHash} and {toHash} in my git log, e.g.:

$ git log --oneline -n 4
178864a sit
dcbc68d dolor
ecddabb ipsum
b8bf8f0 lorem

But when I push a git tag, e.g.:

$ git tag -a 0.1.0 -m "0.1.0"
$ git push origin 0.1.0

...then {fromHash} is the obviously-invalid 0000..., but {toHash} is a not-obviously-invalid value that I cannot reconcile with anything in my git log. E.g.:

{  
  "eventKey":"repo:refs_changed",
  "date":"2017-09-19T09:47:32+1000",
  "actor":{ ...  },
  "repository":{  ...  },
  "changes":[  
    {  
      "ref":{  
        "id":"refs/tags/0.1.0",
        "displayId":"0.1.0",
        "type":"TAG"
      },
      "refId":"refs/tags/0.1.0",
      "fromHash":"0000000000000000000000000000000000000000",
      "toHash":"b82dd854c413d8e09aaf68c3c286f11ec6780be6",
      "type":"ADD"
    }
  ]
}

The git log output remains unchanged in my shell, so what does the {toHash} value of b82dd85... represent?

Answer 1

The toHash represents the SHA of the annotated tag you created with git tag -a ... You can see both the commit id and the SHA of the tag object with git show-ref --tags -d:

In your case it should show something like this

$ git show-ref --tags -d | grep 0.1.0

b82dd854c413d8e09aaf68c3c286f11ec6780be6 refs/tags/0.1.0
178864a7d521b6f5e720b386b2c2b0ef8563e0dc refs/tags/0.1.0^{}