Merge branch 'rs/branch-del-symref' into next
A symbolic ref refs/heads/SYM was not correctly removed with
"git branch -d SYM"; the command removed the ref pointed by
SYM instead.
Will merge to 'master' in the second batch after 1.8.0 ships.
* rs/branch-del-symref:
branch: show targets of deleted symrefs, not sha1s
branch: skip commit checks when deleting symref branches
branch: delete symref branch, not its target
branch: factor out delete_branch_config()
branch: factor out check_branch_commit()