bug: message format template does not receive documented variables

[macrozone]

according to https://github.com/semantic-release/git#message

multiple variables are available, eg. branch.type (what i desperatly need), but this seems to have been broken.

in https://github.com/semantic-release/git/blob/master/lib/prepare.js#L65

its clear that these variables are not available. Worse: branch has been overwritten with branch.name. So without breaking, we cannot re-introduce the branch variable to access branch.type etc. On the other hand, the current behaviour is not documented and therefore might not be intended

[macrozone]

would be nice if someone could look at my mr