Env var handling should prefer old names

For back-compat, if we find both an old and new env var for the same
flag, prefer the old.  This matters because the docker image sets
GITSYNC_ROOT but some users still set GIT_SYNC_ROOT.

Fix up CI for GH app tests

For now we skip

Add lint for shellcheck, fix issues

Merge pull request #872 from kubernetes/dependabot/github_actions/gol…

…angci/golangci-lint-action-5

Bump golangci/golangci-lint-action from 4 to 5

Merge pull request #870 from demoth/patch-1

README.md - fix usage comments

Fix staging script

Better error handling in case of failed commands.

Match "vdso" and "vdso64".

Add '-F none' to e2e git SSH command for weird environments

e2e: use global 'user.email' config

Merge pull request #794 from thockin/master

Add /tmp to staging

Merge pull request #794 from thockin/master

Add /tmp to staging