[dajiaohuang]

Problem

-ignore-private was enforced only while cloning a new repository. When a private repository already existed in the backup directory, backUp selected updateExistingRepo first, so it was still updated despite the exclusion option.

Change

Skip private repositories at the start of backUp, before checking the destination path. This applies the option to both new and existing backups. The regression test uses an in-memory filesystem and a synthetic failing Git command to prove an existing private repository is not updated.

Verification

• Focused backup tests passed.
• go test -mod=readonly . -skip 'ArchiveDownloadFail' -count=1 passed on Go 1.26.3 / Windows amd64. The two excluded archive-failure tests redirect to 127.0.0.1:8080; they were not run to avoid contacting a potentially live local service.
• gofmt -d backup.go backup_test.go and git diff --check passed.

[amitsaha]

@dajiaohuang thanks for the PR. Can i confirm you verified the fix with a real run with one of the supported git hosts?

[dajiaohuang]

No—I did not verify it with a real supported Git host. I reproduced the existing-backup path with a synthetic in-memory regression and ran the focused tests plus the safe package suite. I did not run an actual backup job or clone against a remote host/account, so real-host behavior remains unverified.