kernel/git - git - PowerEL Git System

Author	SHA1	Message	Date
Jeff King	daf7d86783	silence broken link warnings with revs->ignore_missing_links We set revs->ignore_missing_links to instruct the revision-walking machinery that we know the history graph may be incomplete. For example, we use it when walking unreachable but recent objects; we want to add what we can, but it's OK if the history is incomplete. However, we still print error messages for the missing objects, which can be confusing. This is not an error, but just a normal situation when transitioning from a repository last pruned by an older git (which can leave broken segments of history) to a more recent one (where we try to preserve whole reachable segments). Signed-off-by: Jeff King <peff@peff.net> Signed-off-by: Junio C Hamano <gitster@pobox.com>	10 years ago
Jeff King	33d4221c79	write_sha1_file: freshen existing objects When we try to write a loose object file, we first check whether that object already exists. If so, we skip the write as an optimization. However, this can interfere with prune's strategy of using mtimes to mark files in progress. For example, if a branch contains a particular tree object and is deleted, that tree object may become unreachable, and have an old mtime. If a new operation then tries to write the same tree, this ends up as a noop; we notice we already have the object and do nothing. A prune running simultaneously with this operation will see the object as old, and may delete it. We can solve this by "freshening" objects that we avoid writing by updating their mtime. The algorithm for doing so is essentially the same as that of has_sha1_file. Therefore we provide a new (static) interface "check_and_freshen", which finds and optionally freshens the object. It's trivial to implement freshening and simple checking by tweaking a single parameter. Signed-off-by: Jeff King <peff@peff.net> Signed-off-by: Junio C Hamano <gitster@pobox.com>	11 years ago
Jeff King	abcb86553d	pack-objects: match prune logic for discarding objects 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: Jeff King <peff@peff.net> Signed-off-by: Junio C Hamano <gitster@pobox.com>	11 years ago
Jeff King	d3038d22f9	prune: keep objects reachable from recent objects 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: Jeff King <peff@peff.net> Signed-off-by: Junio C Hamano <gitster@pobox.com>	11 years ago