Fix manually building specific tag.

If a tag was specified, the tag information would not be determined.
Fix using clone source instead of used repo.

Source for unpacking, as well as summary git object.
Remove --repo option. Superceded by config file.
Remove environment var remnants; add --tmpbase.

Note that this adds bcprovPath to the freenetrc, so older ones will have
to be updated to include it.
Whitespace.
Remove needless check.
Remove needless braces.

Braces are only needed to avoid ambiguity in parameter names. There is
no ambiguity in these cases.