That explains why it was added to git/contrib. It seems to have moved out of contrib with essentially no discussion.
The original commit adding it to contrib anticipated moving parts of it into git proper:
For example, we previously discussed the idea of a "git big-clone" that does
much of what "scalar clone" is doing. This patch series is a step to make
such functionality exist in the Git code base while we simmer on what such a
"git big-clone" command-line interface would look like.
This is one of many possible ways to do this. Creating a 'git big-clone'
could lock Git into backwards compatibility concerns so it is necessary to
approach such an endeavor with caution.
Seems like now it is locked into backwards compatability concerns around including the scalar command.
