Closes:#867693.
* dgit: Cope if the archive server sends an HTTP redirect,
by passing -L to curl. Closes:#867185,#867309.
+ * dgit: Cope with newer git which hates --local outside a working
+ tree. Closes:#865863.
* dgit: rpush: Honour local git config from build host working
tree.
* test suite: Cope with git restricting ext:: protocols.