Add shellfirm rules for git checkout -- . and git restore .

[kaplanelad]

• Add git:checkout_discard_all rule to catch git checkout -- . and git checkout -- *
• Add git:restore_discard_all rule to catch git restore ., git restore --staged ., and git restore *
• Both rules allow specific file targets (e.g. git restore file.txt)
• 22 new test cases covering positive and negative matches