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2017-05-23ref_update_reject_duplicates(): expose function to whole refs moduleLibravatar Michael Haggerty1-0/+8
It will soon have some other users. Signed-off-by: Michael Haggerty <mhagger@alum.mit.edu> Signed-off-by: Junio C Hamano <gitster@pobox.com>
2017-05-23ref_transaction_prepare(): new optional step for reference updatesLibravatar Michael Haggerty1-10/+35
In the future, compound reference stores will sometimes need to modify references in two different reference stores at the same time, meaning that a single logical reference transaction might have to be implemented as two internal sub-transactions. They won't want to call `ref_transaction_commit()` for the two sub-transactions one after the other, because that wouldn't be atomic (the first commit could succeed and the second one fail). Instead, they will want to prepare both sub-transactions (i.e., obtain any necessary locks and do any pre-checks), and only if both prepare steps succeed, then commit both sub-transactions. Start preparing for that day by adding a new, optional `ref_transaction_prepare()` step to the reference transaction sequence, which obtains the locks and does any prechecks, reporting any errors that occur. Also add a `ref_transaction_abort()` function that can be used to abort a sub-transaction even if it has already been prepared. That is on the side of the public-facing API. On the side of the `ref_store` VTABLE, get rid of `transaction_commit` and instead add methods `transaction_prepare`, `transaction_finish`, and `transaction_abort`. A `ref_transaction_commit()` now basically calls methods `transaction_prepare` then `transaction_finish`. Signed-off-by: Michael Haggerty <mhagger@alum.mit.edu> Signed-off-by: Junio C Hamano <gitster@pobox.com>
2017-05-23ref_store: take a `msg` parameter when deleting referencesLibravatar Michael Haggerty1-1/+1
Just because the files backend can't retain reflogs for deleted references is no reason that they shouldn't be supported by the virtual method interface. Also, `delete_ref()` and `refs_delete_ref()` have already gained `msg` parameters. Now let's add them to `delete_refs()` and `refs_delete_refs()`. Signed-off-by: Michael Haggerty <mhagger@alum.mit.edu> Signed-off-by: Junio C Hamano <gitster@pobox.com>
2017-05-23ref_iterator_begin_fn(): fix docstringLibravatar Michael Haggerty1-3/+4
The iterator returned by this function only includes references whose names start with the whole prefix, not all of those in `find_containing_dir(prefix)` as the old docstring claimed. This docstring was probably copy-pasted from old ref-cache code, which had the old specification. But now, `cache_ref_iterator_begin()` (from which the files reference iterator gets its values) automatically wraps its output using `prefix_ref_iterator_begin()` when necessary, so it has the stricter behavior. Signed-off-by: Michael Haggerty <mhagger@alum.mit.edu> Signed-off-by: Junio C Hamano <gitster@pobox.com>
2017-05-23Merge branch 'bc/object-id'Libravatar Junio C Hamano1-2/+2
* bc/object-id: (53 commits) object: convert parse_object* to take struct object_id tree: convert parse_tree_indirect to struct object_id sequencer: convert do_recursive_merge to struct object_id diff-lib: convert do_diff_cache to struct object_id builtin/ls-tree: convert to struct object_id merge: convert checkout_fast_forward to struct object_id sequencer: convert fast_forward_to to struct object_id builtin/ls-files: convert overlay_tree_on_cache to object_id builtin/read-tree: convert to struct object_id sha1_name: convert internals of peel_onion to object_id upload-pack: convert remaining parse_object callers to object_id revision: convert remaining parse_object callers to object_id revision: rename add_pending_sha1 to add_pending_oid http-push: convert process_ls_object and descendants to object_id refs/files-backend: convert many internals to struct object_id refs: convert struct ref_update to use struct object_id ref-filter: convert some static functions to struct object_id Convert struct ref_array_item to struct object_id Convert the verify_pack callback to struct object_id Convert lookup_tag to struct object_id ...
2017-05-16Merge branch 'nd/worktree-kill-parse-ref'Libravatar Junio C Hamano1-0/+4
"git gc" did not interact well with "git worktree"-managed per-worktree refs. * nd/worktree-kill-parse-ref: refs: kill set_worktree_head_symref() worktree.c: kill parse_ref() in favor of refs_resolve_ref_unsafe() refs: introduce get_worktree_ref_store() refs: add REFS_STORE_ALL_CAPS refs.c: make submodule ref store hashmap generic environment.c: fix potential segfault by get_git_common_dir()
2017-05-08refs: convert struct ref_update to use struct object_idLibravatar brian m. carlson1-2/+2
Convert struct ref_array_item to use struct object_id by changing the definition and applying the following semantic patch, plus the standard object_id transforms: @@ struct ref_update E1; @@ - E1.new_sha1 + E1.new_oid.hash @@ struct ref_update *E1; @@ - E1->new_sha1 + E1->new_oid.hash @@ struct ref_update E1; @@ - E1.old_sha1 + E1.old_oid.hash @@ struct ref_update *E1; @@ - E1->old_sha1 + E1->old_oid.hash This transformation allows us to convert write_ref_to_lockfile, which is required to convert parse_object. Signed-off-by: brian m. carlson <sandals@crustytoothpaste.net> Signed-off-by: Junio C Hamano <gitster@pobox.com>
2017-04-24refs: add REFS_STORE_ALL_CAPSLibravatar Nguyễn Thái Ngọc Duy1-0/+4
Signed-off-by: Nguyễn Thái Ngọc Duy <pclouds@gmail.com> Signed-off-by: Junio C Hamano <gitster@pobox.com>
2017-04-16refs_verify_refname_available(): implement once for all backendsLibravatar Michael Haggerty1-7/+0
It turns out that we can now implement `refs_verify_refname_available()` based on the other virtual functions, so there is no need for it to be defined at the backend level. Instead, define it once in `refs.c` and remove the `files_backend` definition. Signed-off-by: Michael Haggerty <mhagger@alum.mit.edu> Signed-off-by: Junio C Hamano <gitster@pobox.com>
2017-04-14refs_ref_iterator_begin(): new functionLibravatar Michael Haggerty1-0/+11
Extract a new function from `do_for_each_ref()`. It will be useful elsewhere. Signed-off-by: Michael Haggerty <mhagger@alum.mit.edu> Signed-off-by: Junio C Hamano <gitster@pobox.com>
2017-04-14refs_read_raw_ref(): new functionLibravatar Michael Haggerty1-0/+4
Extract a new function from `refs_resolve_ref_unsafe()`. It will be useful elsewhere. Signed-off-by: Michael Haggerty <mhagger@alum.mit.edu> Signed-off-by: Junio C Hamano <gitster@pobox.com>
2017-04-14refs: new transaction related ref-store apiLibravatar Nguyễn Thái Ngọc Duy1-0/+1
The transaction struct now takes a ref store at creation and will operate on that ref store alone. Signed-off-by: Nguyễn Thái Ngọc Duy <pclouds@gmail.com> Signed-off-by: Junio C Hamano <gitster@pobox.com>
2017-04-14refs: add new ref-store apiLibravatar Nguyễn Thái Ngọc Duy1-28/+3
This is not meant to cover all existing API. It adds enough to test ref stores with the new test program test-ref-store, coming soon and to be used by files-backend.c. Signed-off-by: Nguyễn Thái Ngọc Duy <pclouds@gmail.com> Signed-off-by: Junio C Hamano <gitster@pobox.com>
2017-04-14refs: rename get_ref_store() to get_submodule_ref_store() and make it publicLibravatar Nguyễn Thái Ngọc Duy1-12/+0
This function is intended to replace *_submodule() refs API. It provides a ref store for a specific submodule, which can be operated on by a new set of refs API. Signed-off-by: Nguyễn Thái Ngọc Duy <pclouds@gmail.com> Signed-off-by: Junio C Hamano <gitster@pobox.com>
2017-04-14files-backend: replace submodule_allowed check in files_downcast()Libravatar Nguyễn Thái Ngọc Duy1-1/+8
files-backend.c is unlearning submodules. Instead of having a specific check for submodules to see what operation is allowed, files backend now takes a set of flags at init. Each operation will check if the required flags is present before performing. For now we have four flags: read, write and odb access. Main ref store has all flags, obviously, while submodule stores are read-only and have access to odb (*). The "main" flag stays because many functions in the backend calls frontend ones without a ref store, so these functions always target the main ref store. Ideally the flag should be gone after ref-store-aware api is in place and used by backends. (*) Submodule code needs for_each_ref. Try take REF_STORE_ODB flag out. At least t3404 would fail. The "have access to odb" in submodule is a bit hacky since we don't know from he whether add_submodule_odb() has been called. Signed-off-by: Nguyễn Thái Ngọc Duy <pclouds@gmail.com> Signed-off-by: Junio C Hamano <gitster@pobox.com>
2017-03-27refs: move submodule code out of files-backend.cLibravatar Nguyễn Thái Ngọc Duy1-5/+4
files-backend is now initialized with a $GIT_DIR. Converting a submodule path to where real submodule gitdir is located is done in get_ref_store(). This gives a slight performance improvement for submodules since we don't convert submodule path to gitdir at every backend call like before. We pay that once at ref-store creation. More cleanup in files_downcast() and files_assert_main_repository() follows shortly. It's separate to keep noises from this patch. Signed-off-by: Nguyễn Thái Ngọc Duy <pclouds@gmail.com> Signed-off-by: Junio C Hamano <gitster@pobox.com>
2017-03-27files-backend: make files_log_ref_write() staticLibravatar Nguyễn Thái Ngọc Duy1-4/+0
Created in 5f3c3a4e6f (files_log_ref_write: new function - 2015-11-10) but probably never used outside refs-internal.c Signed-off-by: Nguyễn Thái Ngọc Duy <pclouds@gmail.com> Signed-off-by: Junio C Hamano <gitster@pobox.com>
2017-02-27Merge branch 'mh/submodule-hash'Libravatar Junio C Hamano1-41/+7
Code and design clean-up for the refs API. * mh/submodule-hash: read_loose_refs(): read refs using resolve_ref_recursively() files_ref_store::submodule: use NULL for the main repository base_ref_store_init(): remove submodule argument refs: push the submodule attribute down refs: store submodule ref stores in a hashmap register_ref_store(): new function refs: remove some unnecessary handling of submodule == "" refs: make some ref_store lookup functions private refs: reorder some function definitions
2017-02-27Merge branch 'mh/ref-remove-empty-directory'Libravatar Junio C Hamano1-7/+15
Deletion of a branch "foo/bar" could remove .git/refs/heads/foo once there no longer is any other branch whose name begins with "foo/", but we didn't do so so far. Now we do. * mh/ref-remove-empty-directory: (23 commits) files_transaction_commit(): clean up empty directories try_remove_empty_parents(): teach to remove parents of reflogs, too try_remove_empty_parents(): don't trash argument contents try_remove_empty_parents(): rename parameter "name" -> "refname" delete_ref_loose(): inline function delete_ref_loose(): derive loose reference path from lock log_ref_write_1(): inline function log_ref_setup(): manage the name of the reflog file internally log_ref_write_1(): don't depend on logfile argument log_ref_setup(): pass the open file descriptor back to the caller log_ref_setup(): improve robustness against races log_ref_setup(): separate code for create vs non-create log_ref_write(): inline function rename_tmp_log(): improve error reporting rename_tmp_log(): use raceproof_create_file() lock_ref_sha1_basic(): use raceproof_create_file() lock_ref_sha1_basic(): inline constant raceproof_create_file(): new function safe_create_leading_directories(): set errno on SCLD_EXISTS safe_create_leading_directories_const(): preserve errno ...
2017-02-13read_loose_refs(): read refs using resolve_ref_recursively()Libravatar Michael Haggerty1-0/+5
There is no need to call read_ref_full() or resolve_gitlink_ref() from read_loose_refs(), because we already have a ref_store object in hand. So we can call resolve_ref_recursively() ourselves. Happily, this unifies the code for the submodule vs. non-submodule cases. This requires resolve_ref_recursively() to be exposed to the refs subsystem, though not to non-refs code. Signed-off-by: Michael Haggerty <mhagger@alum.mit.edu> Reviewed-by: Jeff King <peff@peff.net> Signed-off-by: Junio C Hamano <gitster@pobox.com>
2017-02-10base_ref_store_init(): remove submodule argumentLibravatar Michael Haggerty1-4/+3
This is another step towards weakening the 1:1 relationship between ref_stores and submodules. Signed-off-by: Michael Haggerty <mhagger@alum.mit.edu> Reviewed-by: Jeff King <peff@peff.net> Signed-off-by: Junio C Hamano <gitster@pobox.com>
2017-02-10refs: push the submodule attribute downLibravatar Michael Haggerty1-13/+0
Push the submodule attribute down from ref_store to files_ref_store. This is another step towards loosening the 1:1 connection between ref_stores and submodules. Signed-off-by: Michael Haggerty <mhagger@alum.mit.edu> Reviewed-by: Jeff King <peff@peff.net> Signed-off-by: Junio C Hamano <gitster@pobox.com>
2017-02-10refs: store submodule ref stores in a hashmapLibravatar Michael Haggerty1-6/+0
Aside from scaling better, this means that the submodule name needn't be stored in the ref_store instance anymore (which will be changed in a moment). This, in turn, will help loosen the strict 1:1 relationship between ref_stores and submodules. Signed-off-by: Michael Haggerty <mhagger@alum.mit.edu> Reviewed-by: Jeff King <peff@peff.net> Signed-off-by: Junio C Hamano <gitster@pobox.com>
2017-02-10refs: make some ref_store lookup functions privateLibravatar Michael Haggerty1-19/+0
The following functions currently don't need to be exposed: * ref_store_init() * lookup_ref_store() That might change in the future, but for now make them private. Signed-off-by: Michael Haggerty <mhagger@alum.mit.edu> Reviewed-by: Jeff King <peff@peff.net> Signed-off-by: Junio C Hamano <gitster@pobox.com>
2017-01-31refs: add option core.logAllRefUpdates = alwaysLibravatar Cornelius Weig1-2/+0
When core.logallrefupdates is true, we only create a new reflog for refs that are under certain well-known hierarchies. The reason is that we know that some hierarchies (like refs/tags) are not meant to change, and that unknown hierarchies might not want reflogs at all (e.g., a hypothetical refs/foo might be meant to change often and drop old history immediately). However, sometimes it is useful to override this decision and simply log for all refs, because the safety and audit trail is more important than the performance implications of keeping the log around. This patch introduces a new "always" mode for the core.logallrefupdates option which will log updates to everything under refs/, regardless where in the hierarchy it is (we still will not log things like ORIG_HEAD and FETCH_HEAD, which are known to be transient). Based-on-patch-by: Jeff King <peff@peff.net> Signed-off-by: Cornelius Weig <cornelius.weig@tngtech.com> Reviewed-by: Jeff King <peff@peff.net> Signed-off-by: Junio C Hamano <gitster@pobox.com>
2017-01-07files_transaction_commit(): clean up empty directoriesLibravatar Michael Haggerty1-2/+9
When deleting/pruning references, remove any directories that are made empty by the deletion of loose references or of reflogs. Otherwise such empty directories can survive forever and accumulate over time. (Even 'pack-refs', which is smart enough to remove the parent directories of loose references that it prunes, leaves directories that were already empty.) And now that files_transaction_commit() takes care of deleting the parent directories of loose references that it prunes, we don't have to do that in prune_ref() anymore. This change would be unwise if the *creation* of these directories could race with our deletion of them. But the earlier changes in this patch series made the creation paths robust against races, so now it is safe to tidy them up more aggressively. Signed-off-by: Michael Haggerty <mhagger@alum.mit.edu> Reviewed-by: Jeff King <peff@peff.net> Signed-off-by: Junio C Hamano <gitster@pobox.com>
2017-01-07refname_is_safe(): correct docstringLibravatar Michael Haggerty1-5/+6
The behavior of refname_is_safe() was changed in e40f355 "refname_is_safe(): insist that the refname already be normalized", 2016-04-27 without a corresponding update to its docstring. The function is in fact stricter than documented, because it now insists that the result of normalizing the part of a refname following "refs/" is identical to that part of the original refname. Fix the docstring. Signed-off-by: Michael Haggerty <mhagger@alum.mit.edu> Reviewed-by: Jeff King <peff@peff.net> Signed-off-by: Junio C Hamano <gitster@pobox.com>
2016-09-09refs: implement iteration over only per-worktree refsLibravatar David Turner1-1/+9
Alternate refs backends might still use files to store per-worktree refs. So provide a way to iterate over only the per-worktree references in a ref_store. The other backend can set up a files ref_store and iterate using the new DO_FOR_EACH_PER_WORKTREE_ONLY flag when iterating. 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>
2016-09-09refs: make lock genericLibravatar David Turner1-1/+1
Instead of including a files-backend-specific struct ref_lock, change the generic ref_update struct to include a void pointer that backends can use for their own arbitrary data. 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>
2016-09-09refs: add method to rename refsLibravatar David Turner1-0/+4
This removes the last caller of function get_files_ref_store(), so remove it. 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>
2016-09-09refs: add methods to init refs dbLibravatar David Turner1-0/+3
Alternate refs backends might not need the refs/heads directory and so on, so we make ref db initialization part of the backend. 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>
2016-09-09refs: make delete_refs() virtualLibravatar David Turner1-0/+3
In the file-based backend, delete_refs has some special optimization to deal with packed refs. In other backends, we might be able to make ref deletion faster by putting all deletions into a single transaction. So we need a special backend function for this. 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>
2016-09-09refs: add method for initial ref transaction commitLibravatar David Turner1-0/+1
Signed-off-by: Ronnie Sahlberg <rsahlberg@google.com> 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>
2016-09-09refs: add methods for reflogLibravatar David Turner1-7/+37
In the file-based backend, the reflog piggybacks on the ref lock. Since other backends won't have the same sort of ref lock, ref backends must also handle reflogs. Signed-off-by: Ronnie Sahlberg <rsahlberg@google.com> 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>
2016-09-09refs: add method iterator_beginLibravatar Michael Haggerty1-12/+12
Signed-off-by: Michael Haggerty <mhagger@alum.mit.edu> Signed-off-by: Junio C Hamano <gitster@pobox.com>
2016-09-09files_ref_iterator_begin(): take a ref_store argumentLibravatar Michael Haggerty1-4/+4
Signed-off-by: Michael Haggerty <mhagger@alum.mit.edu> Signed-off-by: Junio C Hamano <gitster@pobox.com>
2016-09-09refs: make peel_ref() virtualLibravatar Michael Haggerty1-0/+3
For now it only supports the main reference store. Signed-off-by: Michael Haggerty <mhagger@alum.mit.edu> Signed-off-by: Junio C Hamano <gitster@pobox.com>
2016-09-09refs: make create_symref() virtualLibravatar Michael Haggerty1-0/+5
Signed-off-by: Michael Haggerty <mhagger@alum.mit.edu> Signed-off-by: Junio C Hamano <gitster@pobox.com>
2016-09-09refs: make pack_refs() virtualLibravatar Michael Haggerty1-0/+4
Signed-off-by: Michael Haggerty <mhagger@alum.mit.edu> Signed-off-by: Junio C Hamano <gitster@pobox.com>
2016-09-09refs: make verify_refname_available() virtualLibravatar Michael Haggerty1-0/+7
Signed-off-by: Michael Haggerty <mhagger@alum.mit.edu> Signed-off-by: Junio C Hamano <gitster@pobox.com>
2016-09-09refs: make read_raw_ref() virtualLibravatar Michael Haggerty1-17/+19
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>
2016-09-09read_raw_ref(): take a (struct ref_store *) argumentLibravatar Michael Haggerty1-3/+6
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>
2016-09-09refs: add a transaction_commit() methodLibravatar Ronnie Sahlberg1-0/+5
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>
2016-09-09refs: create a base class "ref_store" for files_ref_storeLibravatar Michael Haggerty1-0/+78
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>
2016-09-09refs: add a backend method structureLibravatar Ronnie Sahlberg1-0/+8
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>
2016-09-09rename_ref_available(): add docstringLibravatar David Turner1-1/+11
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>
2016-06-20for_each_reflog(): reimplement using iteratorsLibravatar Michael Haggerty1-0/+7
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>
2016-06-20do_for_each_ref(): reimplement using reference iterationLibravatar Michael Haggerty1-12/+23
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>
2016-06-20refs: introduce an iterator interfaceLibravatar Michael Haggerty1-0/+194
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>
2016-06-20refs: use name "prefix" consistentlyLibravatar Michael Haggerty1-7/+7
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>