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Commit Graph

Author	SHA1	Message	Date
Michael Haggerty	e1e33b722c	refs: make read_raw_ref() virtual Reference backends will be able to customize this function to implement reference reading. Signed-off-by: Michael Haggerty <mhagger@alum.mit.edu> Signed-off-by: Junio C Hamano <gitster@pobox.com>	9 years ago
Michael Haggerty	34c7ad8ffc	read_raw_ref(): take a (struct ref_store *) argument And make the function work for submodules. Signed-off-by: Michael Haggerty <mhagger@alum.mit.edu> Signed-off-by: Junio C Hamano <gitster@pobox.com>	9 years ago
Ronnie Sahlberg	127b42a186	refs: add a transaction_commit() method Signed-off-by: Ronnie Sahlberg <sahlberg@google.com> Signed-off-by: David Turner <dturner@twopensource.com> Signed-off-by: Junio C Hamano <gitster@pobox.com> Signed-off-by: Jeff King <peff@peff.net> Signed-off-by: Michael Haggerty <mhagger@alum.mit.edu> Signed-off-by: Junio C Hamano <gitster@pobox.com>	9 years ago
Michael Haggerty	00eebe351c	refs: create a base class "ref_store" for files_ref_store We want ref_stores to be polymorphic, so invent a base class of which files_ref_store is a derived class. For now there is exactly one ref_store for the main repository and one for any submodules whose references have been accessed. Signed-off-by: Michael Haggerty <mhagger@alum.mit.edu> Signed-off-by: Junio C Hamano <gitster@pobox.com>	9 years ago
Ronnie Sahlberg	3dce444f17	refs: add a backend method structure Add a `struct ref_storage_be` to represent types of reference stores. In OO notation, this is the class, and will soon hold some class methods (e.g., a factory to create new ref_store instances) and will also serve as the vtable for ref_store instances of that type. As yet, the backends cannot do anything. Signed-off-by: Ronnie Sahlberg <sahlberg@google.com> Signed-off-by: David Turner <dturner@twopensource.com> Signed-off-by: Junio C Hamano <gitster@pobox.com> Signed-off-by: Jeff King <peff@peff.net> Signed-off-by: Michael Haggerty <mhagger@alum.mit.edu> Signed-off-by: Junio C Hamano <gitster@pobox.com>	9 years ago
David Turner	ff3a299c45	rename_ref_available(): add docstring And improve the internal variable names. Signed-off-by: David Turner <dturner@twopensource.com> Signed-off-by: Junio C Hamano <gitster@pobox.com> Signed-off-by: Michael Haggerty <mhagger@alum.mit.edu> Signed-off-by: Junio C Hamano <gitster@pobox.com>	9 years ago
Michael Haggerty	2880d16f09	for_each_reflog(): reimplement using iterators Allow references with reflogs to be iterated over using a ref_iterator. The latter is implemented as a files_reflog_iterator, which in turn uses dir_iterator to read the "logs" directory. Note that reflog iteration doesn't correctly handle per-worktree reflogs (either before or after this patch). Signed-off-by: Ramsay Jones <ramsay@ramsayjones.plus.com> Signed-off-by: Michael Haggerty <mhagger@alum.mit.edu> Signed-off-by: Junio C Hamano <gitster@pobox.com>	9 years ago
Michael Haggerty	4c4de89573	do_for_each_ref(): reimplement using reference iteration Use the reference iterator interface to implement do_for_each_ref(). Delete a bunch of code supporting the old for_each_ref() implementation. And now that do_for_each_ref() is generic code (it is no longer tied to the files backend), move it to refs.c. The implementation is via a new function, do_for_each_ref_iterator(), which takes a reference iterator as argument and calls a callback function for each of the references in the iterator. This change requires the current_ref performance hack for peel_ref() to be implemented via ref_iterator_peel() rather than peel_entry() because we don't have a ref_entry handy (it is hidden under three layers: file_ref_iterator, merge_ref_iterator, and cache_ref_iterator). So: * do_for_each_ref_iterator() records the active iterator in current_ref_iter while it is running. * peel_ref() checks whether current_ref_iter is pointing at the requested reference. If so, it asks the iterator to peel the reference (which it can do efficiently via its "peel" virtual function). For extra safety, we do the optimization only if the refname addresses are the same, not only if the refname strings are the same, to forestall possible mixups between refnames that come from different ref_iterators. Please note that this optimization of peel_ref() is only available when iterating via do_for_each_ref_iterator() (including all of the for_each_ref() functions, which call it indirectly). It would be complicated to implement a similar optimization when iterating directly using a reference iterator, because multiple reference iterators can be in use at the same time, with interleaved calls to ref_iterator_advance(). (In fact we do exactly that in merge_ref_iterator.) But that is not necessary. peel_ref() is only called while iterating over references. Callers who iterate using the for_each_ref() functions benefit from the optimization described above. Callers who iterate using reference iterators directly have access to the ref_iterator, so they can call ref_iterator_peel() themselves to get an analogous optimization in a more straightforward manner. If we rewrite all callers to use the reference iteration API, then we can remove the current_ref_iter hack permanently. Signed-off-by: Michael Haggerty <mhagger@alum.mit.edu> Signed-off-by: Junio C Hamano <gitster@pobox.com>	9 years ago
Michael Haggerty	3bc581b940	refs: introduce an iterator interface Currently, the API for iterating over references is via a family of for_each_ref()-type functions that invoke a callback function for each selected reference. All of these eventually call do_for_each_ref(), which knows how to do one thing: iterate in parallel through two ref_caches, one for loose and one for packed refs, giving loose references precedence over packed refs. This is rather complicated code, and is quite specialized to the files backend. It also requires callers to encapsulate their work into a callback function, which often means that they have to define and use a "cb_data" struct to manage their context. The current design is already bursting at the seams, and will become even more awkward in the upcoming world of multiple reference storage backends: * Per-worktree vs. shared references are currently handled via a kludge in git_path() rather than iterating over each part of the reference namespace separately and merging the results. This kludge will cease to work when we have multiple reference storage backends. * The current scheme is inflexible. What if we sometimes want to bypass the ref_cache, or use it only for packed or only for loose refs? What if we want to store symbolic refs in one type of storage backend and non-symbolic ones in another? In the future, each reference backend will need to define its own way of iterating over references. The crux of the problem with the current design is that it is impossible to compose for_each_ref()-style iterations, because the flow of control is owned by the for_each_ref() function. There is nothing that a caller can do but iterate through all references in a single burst, so there is no way for it to interleave references from multiple backends and present the result to the rest of the world as a single compound backend. This commit introduces a new iteration primitive for references: a ref_iterator. A ref_iterator is a polymorphic object that a reference storage backend can be asked to instantiate. There are three functions that can be applied to a ref_iterator: * ref_iterator_advance(): move to the next reference in the iteration * ref_iterator_abort(): end the iteration before it is exhausted * ref_iterator_peel(): peel the reference currently being looked at Iterating using a ref_iterator leaves the flow of control in the hands of the caller, which means that ref_iterators from multiple sources (e.g., loose and packed refs) can be composed and presented to the world as a single compound ref_iterator. It also means that the backend code for implementing reference iteration will sometimes be more complicated. For example, the cache_ref_iterator (which iterates over a ref_cache) can't use the C stack to recurse; instead, it must manage its own stack internally as explicit data structures. There is also a lot of boilerplate connected with object-oriented programming in C. Eventually, end-user callers will be able to be written in a more natural way—managing their own flow of control rather than having to work via callbacks. Since there will only be a few reference backends but there are many consumers of this API, this is a good tradeoff. More importantly, we gain composability, and especially the possibility of writing interchangeable parts that can work with any ref_iterator. For example, merge_ref_iterator implements a generic way of merging the contents of any two ref_iterators. It is used to merge loose + packed refs as part of the implementation of the files_ref_iterator. But it will also be possible to use it to merge other pairs of reference sources (e.g., per-worktree vs. shared refs). Another example is prefix_ref_iterator, which can be used to trim a prefix off the front of reference names before presenting them to the caller (e.g., "refs/heads/master" -> "master"). In this patch, we introduce the iterator abstraction and many utilities, and implement a reference iterator for the files ref storage backend. (I've written several other obvious utilities, for example a generic way to filter references being iterated over. These will probably be useful in the future. But they are not needed for this patch series, so I am not including them at this time.) In a moment we will rewrite do_for_each_ref() to work via reference iterators (allowing some special-purpose code to be discarded), and do something similar for reflogs. In future patch series, we will expose the ref_iterator abstraction in the public refs API so that callers can use it directly. Implementation note: I tried abstracting this a layer further to allow generic iterators (over arbitrary types of objects) and generic utilities like a generic merge_iterator. But the implementation in C was very cumbersome, involving (in my opinion) too much boilerplate and too much unsafe casting, some of which would have had to be done on the caller side. However, I did put a few iterator-related constants in a top-level header file, iterator.h, as they will be useful in a moment to implement iteration over directory trees and possibly other types of iterators in the future. Signed-off-by: Ramsay Jones <ramsay@ramsayjones.plus.com> Signed-off-by: Michael Haggerty <mhagger@alum.mit.edu> Signed-off-by: Junio C Hamano <gitster@pobox.com>	9 years ago
Michael Haggerty	4633a846f5	refs: use name "prefix" consistently In the context of the for_each_ref() functions, call the prefix that references must start with "prefix". (In some places it was called "base".) This is clearer, and also prevents confusion with another planned use of the word "base". Signed-off-by: Michael Haggerty <mhagger@alum.mit.edu> Signed-off-by: Junio C Hamano <gitster@pobox.com>	9 years ago
Michael Haggerty	067622b0e8	do_for_each_ref(): move docstring to the header file Signed-off-by: Michael Haggerty <mhagger@alum.mit.edu> Signed-off-by: Junio C Hamano <gitster@pobox.com>	9 years ago
Michael Haggerty	6e30b2f652	lock_ref_for_update(): don't resolve symrefs If a transaction includes a non-NODEREF update to a symbolic reference, we don't have to look it up in lock_ref_for_update(). The reference will be dereferenced anyway when the split-off update is processed. This change requires that we store a backpointer from the split-off update to its parent update, for two reasons: * We still want to report the original reference name in error messages. So if an error occurs when checking the split-off update's old_sha1, walk the parent_update pointers back to find the original reference name, and report that one. * We still need to write the old_sha1 of the symref to its reflog. So after we read the split-off update's reference value, walk the parent_update pointers back and fill in their old_sha1 fields. Aside from eliminating unnecessary reads, this change fixes a subtle (though not very serious) race condition: in the old code, the old_sha1 of the symref was resolved before the reference that it pointed at was locked. So it was possible that the old_sha1 value logged to the symref's reflog could be wrong if another process changed the downstream reference before it was locked. Signed-off-by: Michael Haggerty <mhagger@alum.mit.edu>	9 years ago
Michael Haggerty	92b1551b1d	refs: resolve symbolic refs first Before committing ref updates, split symbolic ref updates into two parts: an update to the underlying ref, and a log-only update to the symbolic ref. This ensures that both references are locked correctly during the transaction, including while their reflogs are updated. Similarly, if the reference pointed to by HEAD is modified directly, add a separate log-only update to HEAD, rather than leaving the job of updating HEAD's reflog to commit_ref_update(). This change ensures that HEAD is locked correctly while its reflog is being modified, as well as being cheaper (HEAD only needs to be resolved once). This makes use of a new function, lock_raw_ref(), which is analogous to read_raw_ref(), but acquires a lock on the reference before reading it. This change still has two problems: * There are redundant read_ref_full() reference lookups. * It is still possible to get incorrect reflogs for symbolic references if there is a concurrent update by another process, since the old_oid of a symref is determined before the lock on the pointed-to ref is held. Both problems will soon be fixed. Signed-off-by: David Turner <dturner@twopensource.com> Signed-off-by: Junio C Hamano <gitster@pobox.com> Signed-off-by: Michael Haggerty <mhagger@alum.mit.edu> WIP	9 years ago
Michael Haggerty	71564516de	add_update(): initialize the whole ref_update Change add_update() to initialize all of the fields in the new ref_update object. Rename the function to ref_transaction_add_update(), and increase its visibility to all of the refs-related code. All of this makes the function more useful for other future callers. Signed-off-by: Michael Haggerty <mhagger@alum.mit.edu>	9 years ago
Michael Haggerty	3a8af7be8f	verify_refname_available(): adjust constness in declaration The two string_list arguments can be const. Signed-off-by: Michael Haggerty <mhagger@alum.mit.edu>	9 years ago
David Turner	d99aa884df	refs: allow log-only updates The refs infrastructure learns about log-only ref updates, which only update the reflog. Later, we will use this to separate symbolic reference resolution from ref updating. Signed-off-by: David Turner <dturner@twopensource.com> Signed-off-by: Junio C Hamano <gitster@pobox.com> Signed-off-by: Michael Haggerty <mhagger@alum.mit.edu>	9 years ago
Michael Haggerty	c52ce248d6	ref_transaction_create(): disallow recursive pruning It is nonsensical (and a little bit dangerous) to use REF_ISPRUNING without REF_NODEREF. Forbid it explicitly. Change the one REF_ISPRUNING caller to pass REF_NODEREF too. Signed-off-by: Michael Haggerty <mhagger@alum.mit.edu>	9 years ago
Michael Haggerty	cf596442c6	read_raw_ref(): move docstring to header file Signed-off-by: Michael Haggerty <mhagger@alum.mit.edu>	9 years ago
Michael Haggerty	92b380931e	read_raw_ref(): rename symref argument to referent After all, it doesn't hold the symbolic reference, but rather the reference referred to. Signed-off-by: Michael Haggerty <mhagger@alum.mit.edu>	9 years ago
Michael Haggerty	3a0b6b9aba	read_raw_ref(): rename flags argument to type This will hopefully reduce confusion with the "flags" arguments that are used in many functions in this module as an input parameter to choose how the function should operate. Signed-off-by: Michael Haggerty <mhagger@alum.mit.edu>	9 years ago
David Turner	2d0663b216	refs: move resolve_ref_unsafe into common code Now that resolve_ref_unsafe's only interaction with the backend is through read_raw_ref, we can move it into the common code. Later, we'll replace read_raw_ref with a backend function. Signed-off-by: David Turner <dturner@twopensource.com> Reviewed-by: Michael Haggerty <mhagger@alum.mit.edu> Signed-off-by: Junio C Hamano <gitster@pobox.com>	9 years ago
David Turner	937705901b	refs: move for_each_ref functions into common code Make do_for_each_ref take a submodule as an argument instead of a ref_cache. Since all for_each_ref functions are defined in terms of do_for_each_ref, we can then move them into the common code. Later, we can simply make do_for_each_ref into a backend function. Signed-off-by: David Turner <dturner@twopensource.com> Reviewed-by: Michael Haggerty <mhagger@alum.mit.edu> Signed-off-by: Junio C Hamano <gitster@pobox.com>	9 years ago
David Turner	0845122c39	refs: break out ref conflict checks Create new function find_descendant_ref, to hold one of the ref conflict checks used in verify_refname_available. Multiple backends will need this function, so move it to the common code. Also move rename_ref_available to the common code, because alternate backends might need it and it has no files-backend-specific code. Signed-off-by: David Turner <dturner@twopensource.com> Signed-off-by: Junio C Hamano <gitster@pobox.com> Signed-off-by: Michael Haggerty <mhagger@alum.mit.edu> Signed-off-by: Jeff King <peff@peff.net>	9 years ago
David Turner	5f3c3a4e6f	files_log_ref_write: new function Because HEAD and stash are per-worktree, every refs backend needs to go through the files backend to write these refs. So create a new function, files_log_ref_write, and add it to refs/refs-internal.h. Later, we will use this to handle reflog updates for per-worktree symbolic refs (HEAD). Signed-off-by: David Turner <dturner@twopensource.com> Signed-off-by: Junio C Hamano <gitster@pobox.com> Signed-off-by: Michael Haggerty <mhagger@alum.mit.edu> Signed-off-by: Jeff King <peff@peff.net>	9 years ago
Michael Haggerty	4cb77009e1	refs/refs-internal.h: new header file There are a number of constants, structs, and static functions defined in refs.c and treated as private to the references module. But we want to support multiple reference backends within the reference module, and those backends will need access to some heretofore private declarations. We don't want those declarations to be visible to non-refs code, so we don't want to move them to refs.h. Instead, add a new header file, refs/refs-internal.h, that is intended to be included only from within the refs module. Make some functions non-static and move some declarations (and their corresponding docstrings) from refs.c to this file. In a moment we will add more content to the "refs" subdirectory. Signed-off-by: Michael Haggerty <mhagger@alum.mit.edu> Signed-off-by: Jeff King <peff@peff.net>	9 years ago

25 Commits (e1e33b722c50c26546335fd5a709f89726c2ea2a)