Merge branch 'db/vcs-helper'

* db/vcs-helper: Makefile: remove remnant of separate http/https/ftp helpers Use a clearer style to issue commands to remote helpers Make the "traditionally-supported" URLs a special case Makefile: install hardlinks for git-remote-<scheme> supported by libcurl if possible Makefile: do not link three copies of git-remote-* programs Makefile: git-http-fetch does not need expat http-fetch: Fix Makefile dependancies Add transport native helper executables to .gitignore git-http-fetch: not a builtin Use an external program to implement fetching with curl Add support for external programs for handling native fetches