libostree v2017.8

[Colin Walters <walters verbum org>]

This is a quicker release closely following 2017.7, but it still
includes a number of changes.  First, a lot of work is landing
from Phillip/Krzesimir for doing "collections" and pulling
content from Avahi/USB drives etc.  That work is still underneath
`--enable-experimental-api`, but look for more from that soon!

Other notable user-visible feature PRs from this cycle are:

`lib/repo: Add min-free-space-percent option, default 3%`: <https://github.com/ostreedev/ostree/pull/987>
`Add "pull --localcache-repo"`: <https://github.com/ostreedev/ostree/pull/982>

An important bugfix for `bare-user` repo mode owners is:
`lib/commit: Ensure bare-user objects are always user-readable`: 
<https://github.com/ostreedev/ostree/pull/989>

Besides that we have a lot of code cleanup, CI work, etc.

Thanks to all contributors!

```
Colin Walters (44):
      main: DevelBuild=yes to `ostree --version` for devel builds
      build-sys: Post-release version bump
      repo: Squash a gcc `-Wmaybe-uninitialized` warning
      ci: Enable -Werror=maybe-uninitialized
      lib/core: Avoid NULL deref in content_file_parse() if out variable unset
      lib/repo: Split archive/bare file parsing
      lib/repo: More cleanup of load_file() internals
      lib/deltas: Port to more to new code style
      cmd/fsck: Port to new style
      tests: add a syntax-check rule for glnx_prefix_error()
      lib/commit: Clean up commit file type handling variables
      lib: Hoist unlinkat() cleanup API to fsutil, use in pull
      lib: Use OtTmpFile for static delta processing
      lib/commit: Fix fallocate size for bare-user symlinks
      lib/ref: Suppress more collection ref methods from introspection
      ci: Make introspection warnings fatal
      lib/deltas: Some style porting
      build: Don't scan ostree-remote.h for introspection if !experimental-api
      pull: Check free space when pulling deltas
      ci: Actually run installed tests again
      Port to GLnxTmpfile
      tree-wide: Misc porting to newer libglnx APIs
      libutil: Add a helper for O_TMPFILE + mmap()
      lib/commit: Refactor non-failable size indexing function
      lib/deltas: More porting to new code style
      lib/repo: Port bareuser-conversion stat to bare load
      lib/pull: Some small style porting
      tests: Fix assert_files_hardlinked
      lib/pull: Don't fetch detached metadata twice for local pulls
      tree-wide: Replace various uses of `archive-z2` → `archive`
      cmdline/pull: Print final status even if noninteractive
      lib: Add a helper to convert struct stat → GFileInfo
      lib/commit: Port a few minor functions to new style
      lib/pull: Move check for requested content earlier
      Add "pull --localcache-repo"
      lib/commit: Fix a tmpfile fd leak in static delta processing
      bin/commit: Port helper functions to new style
      bin/commit: Add '=' to --statoverride
      lib/commit: Ensure bare-user objects are always user-readable
      lib/commit: Use provided length when doing writes
      lib/repo: Add min-free-space-percent option, default 3%
      pull: Cleanly error when doing local pulls of remote-prefixed refs
      lib/repo: Immediately error creating bare-user repo on tmpfs
      Release 2017.8

Jonathan Lebon (6):
      ci: add ci-release-build.sh
      papr: build and test on c7
      test-switchroot.sh: skip if no busybox
      codebase: start using GLNX_HASH_TABLE_FOREACH macros
      ci: unconditionally turn on -Werror
      pull: fix GLNX_HASH_TABLE_FOREACH_KV regressions

Philip Withnall (31):
      build: Add ‘devel’ or ‘release’ to OSTREE_FEATURES for test-symbols.sh
      lib/core: Add ostree_validate_remote_name() for remote names
      lib/core: Fix ‘Since’ line for ostree_validate_remote_name()
      lib/sym: Fix symbol versions for 2017.7 experimental symbols
      lib/remote: Fix ‘Since’ line for OstreeRemote
      lib/repo: Split out ref handling from regenerate_summary()
      lib/ref: Add OstreeCollectionRef type for globally unique refs
      lib/repo: Add collection ID support to OstreeRepo
      lib/refs: Add methods for setting/listing collection–refs
      lib/pull: Add collection support to ostree_repo_pull_with_options()
      lib/repo-finder: Add basic support for finding remote URIs by ref name
      lib/repo-finder: Add config-file based OstreeRepoFinder implementation
      lib/repo-finder: Add mount based OstreeRepoFinder implementation
      lib/bloom: Add an internal bloom filter implementation
      lib/repo-finder: Add Avahi based OstreeRepoFinder implementation
      find-remotes: Add a find-remotes built-in command
      find-remotes: Add pull support to the find-remotes built-in command
      init: Add a --collection-id argument to the built-in init command
      remote-add: Add a --collection-id argument to the built-in add command
      refs: Add a --collections argument to the built-in refs command
      ostree/dump: Include collection IDs and mirrored refs in summary dumps
      ostree/builtins: Add support for collection–refs to a few utilities
      tests: Add integration tests for collections
      lib/refs: Add runtime error checking for collection ID validity
      lib/repo: Fix a typo in a documentation comment
      tests: Fix incorrect `summary --update` usage in test-local-pull.sh
      ostree/summary: Add support for adding additional metadata
      lib/pull: Don’t cache summary file until its signature is verified
      lib/pull: Check whether summary is in normal form when loading it
      lib/pull: Use ostree_repo_verify_summary() to verify summary on pull
      lib/repo: Fix repo-finder deleting remote configs when run

Simon McVittie (1):
      build: Always include ostree-trivial-httpd.xml in tarballs
```

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