git-svn: make dcommit usable for glob users

git-svn: make dcommit usable for glob users

 * dcommit no longer requires the correct -i/GIT_SVN_ID option
   passed to it.  Since you're committing from HEAD (or another
   commit that is a parent of HEAD), you'll be able to find
   a commit with metadata information containing the SVN URL
   that your HEAD was descended from anyways.

 * I don't think dcommit ever worked for people using the
   noMetadata option; so I don't think relying on metadata
   is an issue.

 * useSvmProps users shouldn't commit to SVN::Mirror created
   repositories anyways, right?

 * Users of globbing should automatically be able to commit
   to paths that are not explicitly set in .git/config

Signed-off-by: Eric Wong <normalperson@yhbt.net>