closes #42 by stripping one leading slash from the repo parameter. also fixes a minor issue with the nix develop shellhook. this kinda hacky fix is tested with the following commands: ``` nix build .#repoguard SSH_ORIGINAL_COMMAND="git-upload-pack '/soopy.moe/test-repo'" ./result/bin/repoguard -log-path /tmp/ASDUJBIf-repoguard.log -user git SSH_ORIGINAL_COMMAND="git-upload-pack 'soopy.moe/test-repo'" ./result/bin/repoguard -log-path /tmp/ASDUJBIf-repoguard.log -user git ```