git-svn: allow disabling expensive broken symlink checks

git-svn: allow disabling expensive broken symlink checks

Since dbc6c74d0858d77e61e092a48d467e725211f8e9, git-svn has had
an expensive check for broken symlinks that exist in some
repositories.  This leads to a heavy performance hit on
repositories with many empty blobs that are not supposed to be
symlinks.

The workaround is enabled by default; and may be disabled via:

  git config svn.brokenSymlinkWorkaround false

Reported by Markus Heidelberg.

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