Add git filter support for partial clones

[mschfh]

Please implement support for the git clone --filter flag to enable partial clones.

Additional references:

• https://github.blog/open-source/git/get-up-to-speed-with-partial-clone-and-shallow-clone/
• https://git-scm.com/docs/git-clone#Documentation/git-clone.txt-code--filtercodeemltfilter-specgtem

[mschfh]

@crw Would you consider a contribution/PR for this?

[crw]

@hashicorp/team-ip-compliance please see above. Thanks!

Note that to fix the Terraform issue linked, further work would need to be done in Terraform once this issue was resolved in go-getter.