• Michael Haggerty's avatar
    repack_without_ref(): write peeled refs in the rewritten file · 694b7a19
    Michael Haggerty authored
    When a reference that existed in the packed-refs file is deleted, the
    packed-refs file must be rewritten.  Previously, the file was
    rewritten without any peeled refs, even if the file contained peeled
    refs when it was read.  This was not a bug, because the packed-refs
    file header didn't claim that the file contained peeled values.  But
    it had a performance cost, because the repository would lose the
    benefit of having precomputed peeled references until pack-refs was
    run again.
    
    Teach repack_without_ref() to write peeled refs to the packed-refs
    file (regardless of whether they were present in the old version of
    the file).
    
    This means that if the old version of the packed-refs file was not
    fully peeled, then repack_without_ref() will have to peel references.
    To avoid the expense of reading lots of loose references, we take two
    shortcuts relative to pack-refs:
    
    * If the peeled value of a reference is already known (i.e., because
      it was read from the old version of the packed-refs file), then
      output that peeled value again without any checks.  This is the
      usual code path and should avoid any noticeable overhead.  (This is
      different than pack-refs, which always re-peels references.)
    
    * We don't verify that the packed ref is still current.  It could be
      that a packed references is overridden by a loose reference, in
      which case the packed ref is no longer needed and might even refer
      to an object that has been garbage collected.  But we don't check;
      instead, we just try to peel all references.  If peeling is
      successful, the peeled value is written out (even though it might
      not be needed any more); if not, then the reference is silently
      omitted from the output.
    
    The extra overhead of peeling references in repack_without_ref()
    should only be incurred the first time the packed-refs file is written
    by a version of Git that knows about the "fully-peeled" attribute.
    Signed-off-by: default avatarMichael Haggerty <mhagger@alum.mit.edu>
    Signed-off-by: default avatarJunio C Hamano <gitster@pobox.com>
    694b7a19
t3211-peel-ref.sh 1.96 KB