Merge branch 'rlb/meta'

* rlb/meta:
  t/test-meta.sh: replace 'diff -u5' with 'diff -U5'.
  Don't touch correct target xattrs; remove inappropriate target xattrs.
  Rename test-fs.img to testfs.img and add it to the clean target.
  t/test-meta.sh: detect and handle fakeroot.
  Add atime tests and fix atime capture in metadata.from_path().
  Improve test-meta.sh status messages.
  Handle missing files more gracefully in "bup xstat".
  Add initial (trivial) root-only ACL metadata tests and fix exposed bugs.
  Add initial (trivial) root-only metadata tests for attr and xattr.
  Don't specify 0700 permissions when creating initial directories.
  Fix "meta extract -v" directory output.
  Fix _apply_common_rec() symlink chown/chmod guard.
  Change os.geteuid to os.geteuid() in tmetadata.py.
  Remove redundant call to get_linux_file_attr() in _add_linux_attr().
  In _add_linux_attr(), catch IOError, not EnvironmentError; handle ENOTTY.
  Improve some metadata error messages.
  Only print secs for bup xstat times when ns == 0.
  Use oct() rather than hex() when printing mode from bup xstat.
  Remove bup: prefix from metadata error messages.
  Don't "chmod 000" paths during restore.
  Remove MetadataError and make apply error handling finer-grained.
  Remove MetadataAcquireError and make error handling finer-grained
  Accommodate missing owner or group name during metadata save/restore.
  Preserve existing stack trace when throwing MetadataErrors.
  Add (private for now) "bup xstat" command and use it in the metadata tests.
  Also check defined(_ATFILE_SOURCE) in utimensat() guard.
  Rename bup-meta.1.md to bup-meta.md.
  Simplify FSTime() - always use an integer ns internal representation.
  Rename metadata exceptions and add a parent MetadataError class.
  Don't use str(e) when instantiating Metadata exceptions.
  Fix typos in Metadata._encode_linux_xattr().
  Fix handling of conditional definitions in xstat.
  Always define _have_ns_fs_timestamps (True or False).
  Change "bup meta" to use recursive_dirlist() to add support for --xdev.
  Fix minor bug in "bup meta -t" argument handling (if -> elif).
  Modify drecurse.py and index.py to use xstat functions.
  Move stat-related work to bup.xstat; add xstat.stat.
  Add helpers.fstat and _helpers._have_ns_fs_timestamps.
  Add a helpers.FSTime class to handle filesystem timestamps and use it.
  Attempt to unlink or rmdir existing paths as appropriate during restore.
  Conditionalize build/use of get_linux_file_attr and set_linux_file_attr.
  Check stat() after attempted restore of nonexistent owner/group in tests.
  Don't try to restore owner unless root; handle nonexistent owner/group.
  Add metadata test_restore_restricted_user_group().
  Add helpers.detect_fakeroot() and use it in relevant metadata tests.
  Defer metadata aquisition and application errors during create/extract.
  Rename py_* functions to bup_* in lib/bup/_helpers.c.
  Don't allow negative ns in metadata timestamps; normalize on read/write.
  Add (sec, ns) timestamps and extended stat, lstat, utime, and lutime.
  Add vint tests and signed vint support via write_vint and read_vint.
  Change user to the more accurate owner in metadata.py.
  Correctly respect restore_numeric_ids in Metadata _apply_common_rec().
  Send bup meta --list output to stdout, not stderr.
  Fix bup-meta.1 start-extract/finish-extract example.
  Use Py_RETURN_TRUE in py_lutimes() and py_set_linux_file_attr().
  t/test.sh: fix whitespace problems with the 'Inode:' line from 'stat'.
  t/test.sh: fix occasional atime-related failure in metadata tests.
  t/test.sh: refactoring to reduce duplicated code.
  Add initial support for metadata archives.