Repository cache gets invalidated after several builds

[YrrepNoj]

Related to #1069

When rebuilding a package, zarf will attempt to use repositories that already exist in the ~/.zarf-cache/repos directory. When testing the fix for another (relatively similar issue) I realized that rebuilding the same package multiple times (3+ times) will result in a failure because the HEAD of the repository in the cache directory ends up picking up changes from online-upstream somehow.

Steps to Replicate

Running from the root of the Zarf repo

# make sure the cache is clear
zarf tools clear-cache


# Build all the things!
zarf package create examples/git-data/ --confirm       # This will result with the git repositories being added to the cache
zarf package create examples/git-data/ --confirm       # This will result with the cached repositories having unstaged changes
zarf package create examples/git-data/ --confirm       # This will result in a creation failure

[runyontr]

Looking forward to this fix