1. 27 Apr, 2017 1 commit
    • Johannes Schindelin's avatar
      timestamp_t: a new data type for timestamps · dddbad72
      Johannes Schindelin authored
      Git's source code assumes that unsigned long is at least as precise as
      time_t. Which is incorrect, and causes a lot of problems, in particular
      where unsigned long is only 32-bit (notably on Windows, even in 64-bit
      versions).
      
      So let's just use a more appropriate data type instead. In preparation
      for this, we introduce the new `timestamp_t` data type.
      
      By necessity, this is a very, very large patch, as it has to replace all
      timestamps' data type in one go.
      
      As we will use a data type that is not necessarily identical to `time_t`,
      we need to be very careful to use `time_t` whenever we interact with the
      system functions, and `timestamp_t` everywhere else.
      Signed-off-by: Johannes Schindelin's avatarJohannes Schindelin <johannes.schindelin@gmx.de>
      Signed-off-by: default avatarJunio C Hamano <gitster@pobox.com>
      dddbad72
  2. 16 Oct, 2014 2 commits
    • Jeff King's avatar
      pack-objects: match prune logic for discarding objects · abcb8655
      Jeff King authored
      A recent commit taught git-prune to keep non-recent objects
      that are reachable from recent ones. However, pack-objects,
      when loosening unreachable objects, tries to optimize out
      the write in the case that the object will be immediately
      pruned. It now gets this wrong, since its rule does not
      reflect the new prune code (and this can be seen by running
      t6501 with a strategically placed repack).
      
      Let's teach pack-objects similar logic.
      Signed-off-by: default avatarJeff King <peff@peff.net>
      Signed-off-by: default avatarJunio C Hamano <gitster@pobox.com>
      abcb8655
    • Jeff King's avatar
      prune: keep objects reachable from recent objects · d3038d22
      Jeff King authored
      Our current strategy with prune is that an object falls into
      one of three categories:
      
        1. Reachable (from ref tips, reflogs, index, etc).
      
        2. Not reachable, but recent (based on the --expire time).
      
        3. Not reachable and not recent.
      
      We keep objects from (1) and (2), but prune objects in (3).
      The point of (2) is that these objects may be part of an
      in-progress operation that has not yet updated any refs.
      
      However, it is not always the case that objects for an
      in-progress operation will have a recent mtime. For example,
      the object database may have an old copy of a blob (from an
      abandoned operation, a branch that was deleted, etc). If we
      create a new tree that points to it, a simultaneous prune
      will leave our tree, but delete the blob. Referencing that
      tree with a commit will then work (we check that the tree is
      in the object database, but not that all of its referred
      objects are), as will mentioning the commit in a ref. But
      the resulting repo is corrupt; we are missing the blob
      reachable from a ref.
      
      One way to solve this is to be more thorough when
      referencing a sha1: make sure that not only do we have that
      sha1, but that we have objects it refers to, and so forth
      recursively. The problem is that this is very expensive.
      Creating a parent link would require traversing the entire
      object graph!
      
      Instead, this patch pushes the extra work onto prune, which
      runs less frequently (and has to look at the whole object
      graph anyway). It creates a new category of objects: objects
      which are not recent, but which are reachable from a recent
      object. We do not prune these objects, just like the
      reachable and recent ones.
      
      This lets us avoid the recursive check above, because if we
      have an object, even if it is unreachable, we should have
      its referent. We can make a simple inductive argument that
      with this patch, this property holds (that there are no
      objects with missing referents in the repository):
      
        0. When we have no objects, we have nothing to refer or be
           referred to, so the property holds.
      
        1. If we add objects to the repository, their direct
           referents must generally exist (e.g., if you create a
           tree, the blobs it references must exist; if you create
           a commit to point at the tree, the tree must exist).
           This is already the case before this patch. And it is
           not 100% foolproof (you can make bogus objects using
           `git hash-object`, for example), but it should be the
           case for normal usage.
      
           Therefore for any sequence of object additions, the
           property will continue to hold.
      
        2. If we remove objects from the repository, then we will
           not remove a child object (like a blob) if an object
           that refers to it is being kept. That is the part
           implemented by this patch.
      
           Note, however, that our reachability check and the
           actual pruning are not atomic. So it _is_ still
           possible to violate the property (e.g., an object
           becomes referenced just as we are deleting it). This
           patch is shooting for eliminating problems where the
           mtimes of dependent objects differ by hours or days,
           and one is dropped without the other. It does nothing
           to help with short races.
      
      Naively, the simplest way to implement this would be to add
      all recent objects as tips to the reachability traversal.
      However, this does not perform well. In a recently-packed
      repository, all reachable objects will also be recent, and
      therefore we have to look at each object twice. This patch
      instead performs the reachability traversal, then follows up
      with a second traversal for recent objects, skipping any
      that have already been marked.
      Signed-off-by: default avatarJeff King <peff@peff.net>
      Signed-off-by: default avatarJunio C Hamano <gitster@pobox.com>
      d3038d22
  3. 08 Nov, 2011 1 commit
  4. 07 Jan, 2007 1 commit