libostree 2018.9

[Colin Walters <walters verbum org>]

https://github.com/ostreedev/ostree/releases/tag/v2018.9

It's been two months since our last release, so this one is slightly
larger than usual (the ~monthly cadence).  It's mostly bugfixes
again, although there were some API additions and new
configuration options.

These new features are things like:

 - Allow disabling pulling from LAN/USB/Internet (#1758)
 - lib/repo: Add an API to get min-free-space-* reserved bytes (#1715)
 - OstreeMutableTree: add _remove method (#1724)
 - repo: Add a checkout option to not hardlink zero-sized files (#1752)
 
 On the bugfix side, nothing major; we have the usual small memory
 leak fixes (yeah, we use GCC autocleanups, but still, this is C).
 Beyond that, good examples of bugfixes are:

 - finalize-staged: Bump timeout to 5 minutes (#1755)
 - deploy: Fix removing /var/.updated with separate /var mount (#1730)
 - src/ostree: Don't delete refs having aliases (#1749)

One notable change in this release is the initrd service
`ostree-prepare-root.service` now runs earlier in the boot process.
This shouldn't actually affect OSes, unless there's extended logic
in the initrd that integrates tightly with OSTree. The use case for this is
better integration with Ignition, which will be used in Fedora CoreOS.
PR: #1759

Another systemd related change is the introduction of a path unit:
`ostree-finalize-staged.path`. This allows the service of the same name
to be path activated instead of explicitly started at deployment staging time.
This release however does not yet rely on this mechanism to give time for
packagers and integrators to adapt to the new unit (e.g. by enabling it in
the systemd presets). A future release will *require* this.
Note that deployment staging is still not the default for libostree, although
at least rpm-ostree now unconditionally uses staging, and while it
generally worked well, we hit issues with people using slower hard drives,
hence the increase in timeout in PR #1755 .
PR: #1740

Another change to call out is:
    lib/commit: Don't chown objects to repo target owner (#1754)
We previously had incomplete support for a process running as uid 0
writing to a repository owned by a non-zero uid, but it was never finished.
This will likely be revisited at a later time.

We also merged:
    lib/grub2: Support Debian-style grub.cfg path (#1714)
from a new contibutor (thanks Felix!).  Who incidentally also
posted recently about new Rust bindings:
    
    https://mail.gnome.org/archives/ostree-list/2018-October/msg00000.html
    https://crates.io/crates/libostree
    
Thanks a lot to all contributors!

```
Colin Walters (12 PRs, 13 commits)
  Post-release version bump (#1705)
  deploy: Fix removing /var/.updated with separate /var mount (#1730)
  lib/commit: Don't copy xattrs for metadata objects (#1736)
  lib/progress: Fix leak of GSource (#1741)
  Only verify OSTREE_MAX_METADATA_SIZE for HTTP fetches (#1744)
  rofiles-fuse: Improve error message for failure to open root (#1747)
  repo: Add a checkout option to not hardlink zero-sized files (#1752)
  checkout: Support --union-identical and --force-copy{,--zerosized} (#1753)
  finalize-staged: Bump timeout to 5 minutes (#1755)
  remount: Refactor to helper function instead of loop (#1760)
  README: Add bindings section (#1762)
  PR: #1757
    sysroot: Add error prefixing to deployment parsing
    sysroot: Update some code to use fstatat_allow_noent API

Dan Nicholson (1 PR, 1 commit)
  lib/commit: Don't chown objects to repo target owner (#1754)

Felix Krull (1 PR, 1 commit)
  lib/grub2: Support Debian-style grub.cfg path (#1714)

Jonathan Lebon (7 PRs, 12 commits)
  ci: Disable f28-rpmostree for now (#1727)
  ci: Bump rpm-ostree tag to 2018.8 (#1728)
  boot: Add ostree-finalize-staged.path (#1740)
  lib/mutable-tree: Port to new style (#1742)
  PR: #1732
    lib/fetcher-curl: Prefix fatal errors with full URL
    lib/fetcher-curl: Drop unnecessary check
    lib/fetcher-util: Mark journaled msgs as LOG_ERR
  PR: #1750
    lib/sysroot-deploy: Write to journal when finalizing
    boot: Add Documentation= lines to services
    boot: Remove [Install] from ostree-finalize-staged
  PR: #1759
    ostree-prepare-root.service: Run earlier in initrd
    ostree-prepare-root.service: Use RemainAfterExit=yes

Laurent Bonnans (1 PR, 1 commit)
  lib/fetcher: Fix some memory leaks in curl fetcher (#1716)

Matthew Leeds (10 PRs, 14 commits)
  avahi: Be robust to missing refs in peer summaries (#1717)
  lib/repo: Clean up OstreeRepo docs (#1725)
  lib/repo: Define a metadata key, ostree.deploy-collection-id (#1726)
  create-usb: Always use archive mode (#1733)
  create-usb: Add a --commit option (#1735)
  bash-completion: Fix --repo autocomplete (#1745)
  man/create-usb: Don't recommend summary updates (#1746)
  PR: #1737
    man/ostree.repo-config: Document locking options
    lib/repo: Fix minor mistake in locking docs
    lib/repo: Allow disabling lock timeout
  PR: #1758
    lib/repo-pull: Disable LAN updates by default
    Allow disabling pulling from LAN/USB/Internet
  PR: #1763
    Rename core.repo-finders to core.default-repo-finders
    lib/repo-pull: Add an explanatory comment

Robert McQueen (1 PR, 1 commit)
  OstreeMutableTree: add _remove method (#1724)

Sinny Kumari (1 PR, 1 commit)
  src/ostree: Don't delete refs having aliases (#1749)

Umang Jain (3 PRs, 6 commits)
  Release 2018.9 (#1761)
  PR: #1715
    lib/repo: Ensure min-free-space* config value doesn't overflow
    Add tests for ostree_repo_get_min_free_space_bytes
    lib/repo: Add an API to get min-free-space-* reserved bytes
  PR: #1722
    tests: Update tests for ostree_repo_get_min_free_space_bytes()
    lib/repo: Separate min-free-space-* calculation from transaction codepath
```