From: author@example.com
To: commits@list.com
Subject: [cbas] 2.1 tag deleted. $old_commit_describe
X-Git-Refname: refs/tags/2.1
X-Git-Reftype: tag
X-Git-Oldrev: $old_commit_hash
X-Git-Newrev: 0000000000000000000000000000000000000000

The tag, 2.1 has been deleted
       was $old_commit_hash (commit)

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$old_commit_hash force update lightweight tag
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