git svn: Support multiple branch and tag paths in the svn repository.

git svn: Support multiple branch and tag paths in the svn repository.

This enables git-svn.perl to read multiple 'branches' and 'tags' entries in
svn-remote config sections.  The init and clone subcommands also support
multiple --branches and --tags arguments.

The branch (and tag) subcommand gets a new argument: --destination (or -d).
This argument is required if there are multiple branches (or tags) entries
configured for the remote Subversion repository.  The argument's value
specifies which branch (or tag) path to use to create the branch (or tag).
The specified value must match the left side (without wildcards) of one of
the branches (or tags) refspecs in the svn-remote's config.

[ew: avoided explicit loop when combining globs with "push"]

Signed-off-by: Marc Branchaud <marcnarc@xiplink.com>
Acked-by: Eric Wong <normalperson@yhbt.net>