git: add functions to invoke Git with and without LFS filters
git: add functions to invoke Git with and without LFS filters

Git LFS invokes Git for various actions internally. The new Git
instance is started with the default Git config and therefore might
invoke another Git LFS "filter-process". That is usually not be desired.

Teach Git LFS to invoke Git with or without LFS filters.

github/git-lfs,github/git-lfs,github/git-lfs