createBackupBranch doesn't properly check for names in use

[maxyu1115]

Currently createBackupBranch attempts to check if the intended backupBranchName is already in use. It does not do what it intends, since it only checks other backup branches.

git-backup-sync/src/extension.ts

Line 184 in 5566ba2

if (backupBranchNames.has(backupBranchName)) {

Instead, it needs to check all branches local and remote, and the branch info file is completely irrelevant : ( I'm sorry