Allow multiple branches for sync operations
Created originally on Bitbucket by czarnyczarodziej (Piotr Klecha)
Mercurial allows repeating the "--branch" option for sync operations (incoming, pull, outgoing, push), but Thg accepts only a single branch in Synchronize tab options ("command injection" like specifing the branch as "branch_name1 --branch branch_name2" doesn't work, sadly).