git-svn: remove redundant slashes from show-ignore

Jonathan Scott Duff wrote: > Recently I tried "git svn showignore" on my parrot repository and it > failed. I tracked it down to the prop_walk() sub. When it recurses, > $path has an extra / on the beginning (i.e., when it recurses, it > tries to get the props for "//apps" instead of "/apps"). I *think* > this is because $path is used in the recursive call rather than $p > (which seems to contain a properly transformed $path). Anyway, I've > attached a patch that works for me and I think is generally the right > thing. Patch-submitted-by: Jonathan Scott Duff Signed-off-by: Eric Wong <normalperson@yhbt.net> Signed-off-by: Junio C Hamano <gitster@pobox.com>