Update `GitProperties` so that the `commit.id` entry is also copied to
`commit.id.full`.

Prior to this commit, when returning full details, the value of
`commit.id` would be replaced with a `Map` containing only `abbriv` as
a key. By  copying the value to a sub-key we ensure that it remains
available both in the FULL and SIMPLE modes.

Fixes gh-11892