branchmap: use a context manager when writing the branchmap This is cleaner and safer. The previous code date from long before we had context manager available.

auto-upgrade: skip the operation if the repository cannot be locked This seems like a fine default behavior for now. If some users wants something more aggressive we can make the behavior configurable in the future. Differential Revision: https://phab.mercurial-scm.org/D12619

auto-upgrade: add a test case where the repository is already locked This show the current behavior when the repository to auto-upgrade is already locked. The current behavior is to abort, which is probably not great. Now that we have a proper test, we can think about the behavior we wants in a later tests. Differential Revision: https://phab.mercurial-scm.org/D12618

wait-on-file: properly wait on any files and symlink This make the utility more useful, for example to wait on a lock file. We also add an explicit -L check since the lock are "weird" symlink. Differential Revision: https://phab.mercurial-scm.org/D12617

debuglock: make the command more useful in non-interactive mode The existing prompt mode simply release the lock immediately in non-interactive mode. That is quite useless in the test so now the non-interactive mode simply wait for a signal. Differential Revision: https://phab.mercurial-scm.org/D12616

auto-upgrade: add a test case with no permission to lock the repository This show the current behavior when the repository is unlockable. The current behavior is to abort, which is probably not great. Now that we have a proper test, we can think about the behavior we want in a later changeset. Differential Revision: https://phab.mercurial-scm.org/D12615

auto-upgrade: introduce a way to auto-upgrade to/from dirstate-v2 This is similar to what we introduced for `share-safe`, but apply to the tracked-hint feature. Differential Revision: https://phab.mercurial-scm.org/D12614