Automated tagging after merge request
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### Description
Relating to the recommended git workflow, it is quite a lot of manual task involved when releasing a project.
### Proposal
There are several slash commands available during `issue` or `merge request` creation helping for fast filling of important information, like `milestone`, `labels` and more.
`Merge request` might have a dedicated command, `tags`, that will tag the merge commit of the targeted branch, most common the `master`.
### Links / references

issue