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Tags are unique unsigned integers that are used to correlate a log entry with the place in the code where it was created.
During development, pass in the __TAG__ sentinel wherever an API needs a tag_t value.
Commit your changes with that sentinel.
At some later point, a designated contributor runs bin/tag.sh --conf bin/tag.conf, which assigns a unique number to each __TAG__ instance.
While that second step can be done at any time, it should be done in a designated branch by designated contributor.
The reason for that is to avoid collisions in bin/tag.conf.
A collision would lead to duplicate tag values.
To run bin\tag.sh there must be no uncommitted changes.