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329 commits

Author SHA1 Message Date
Patrick Steinhardt b567004b4b global: improve const correctness when assigning string constants
We're about to enable `-Wwrite-strings`, which changes the type of
string constants to `const char[]`. Fix various sites where we assign
such constants to non-const variables.

Signed-off-by: Patrick Steinhardt <ps@pks.im>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
2024-06-07 10:30:48 -07:00
Junio C Hamano 16a592f132 Merge branch 'ps/pseudo-ref-terminology'
Terminology to call various ref-like things are getting
straightened out.

* ps/pseudo-ref-terminology:
  refs: refuse to write pseudorefs
  ref-filter: properly distinuish pseudo and root refs
  refs: pseudorefs are no refs
  refs: classify HEAD as a root ref
  refs: do not check ref existence in `is_root_ref()`
  refs: rename `is_special_ref()` to `is_pseudo_ref()`
  refs: rename `is_pseudoref()` to `is_root_ref()`
  Documentation/glossary: define root refs as refs
  Documentation/glossary: clarify limitations of pseudorefs
  Documentation/glossary: redefine pseudorefs as special refs
2024-05-28 11:17:06 -07:00
Junio C Hamano 4beb7a3b06 Merge branch 'kn/ref-transaction-symref'
Updates to symbolic refs can now be made as a part of ref
transaction.

* kn/ref-transaction-symref:
  refs: remove `create_symref` and associated dead code
  refs: rename `refs_create_symref()` to `refs_update_symref()`
  refs: use transaction in `refs_create_symref()`
  refs: add support for transactional symref updates
  refs: move `original_update_refname` to 'refs.c'
  refs: support symrefs in 'reference-transaction' hook
  files-backend: extract out `create_symref_lock()`
  refs: accept symref values in `ref_transaction_update()`
2024-05-20 11:20:04 -07:00
Patrick Steinhardt f1701f279a ref-filter: properly distinuish pseudo and root refs
The ref-filter interfaces currently define root refs as either a
detached HEAD or a pseudo ref. Pseudo refs aren't root refs though, so
let's properly distinguish those ref types.

Signed-off-by: Patrick Steinhardt <ps@pks.im>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
2024-05-15 07:30:52 -07:00
Patrick Steinhardt 31951c2248 refs: classify HEAD as a root ref
Root refs are those refs that live in the root of the ref hierarchy.
Our old and venerable "HEAD" reference falls into this category, but we
don't yet classify it as such in `is_root_ref()`.

Adapt the function to also treat "HEAD" as a root ref. This change is
safe to do for all current callers:

  - `ref_kind_from_refname()` already handles "HEAD" explicitly before
    calling `is_root_ref()`.

  - The "files" and "reftable" backends explicitly call both
    `is_root_ref()` and `is_headref()` together.

This also aligns behaviour or `is_root_ref()` and `is_headref()` such
that we stop checking for ref existence. This changes semantics for our
backends:

  - In the reftable backend we already know that the ref must exist
    because `is_headref()` is called as part of the ref iterator. The
    existence check is thus redundant, and the change is safe to do.

  - In the files backend we use it when populating root refs, where we
    would skip adding the "HEAD" file if it was not possible to resolve
    it. The new behaviour is to instead mark "HEAD" as broken, which
    will cause us to emit warnings in various places.

As there are no callers of `is_headref()` left afer the refactoring, we
can absorb it completely into `is_root_ref()`.

Signed-off-by: Patrick Steinhardt <ps@pks.im>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
2024-05-15 07:30:52 -07:00
Patrick Steinhardt afcd067dad refs: do not check ref existence in is_root_ref()
Before this patch series, root refs except for "HEAD" and our special
refs were classified as pseudorefs. Furthermore, our terminology
clarified that pseudorefs must not be symbolic refs. This restriction
is enforced in `is_root_ref()`, which explicitly checks that a supposed
root ref resolves to an object ID without recursing.

This has been extremely confusing right from the start because (in old
terminology) a ref name may sometimes be a pseudoref and sometimes not
depending on whether it is a symbolic or regular ref. This behaviour
does not seem reasonable at all and I very much doubt that it results in
anything sane.

Last but not least, the current behaviour can actually lead to a
segfault when calling `is_root_ref()` with a reference that either does
not exist or that is a symbolic ref because we never initialized `oid`,
but then read it via `is_null_oid()`.

We have now changed terminology to clarify that pseudorefs are really
only "MERGE_HEAD" and "FETCH_HEAD", whereas all the other refs that live
in the root of the ref hierarchy are just plain refs. Thus, we do not
need to check whether the ref is symbolic or not. In fact, we can now
avoid looking up the ref completely as the name is sufficient for us to
figure out whether something would be a root ref or not.

This change of course changes semantics for our callers. As there are
only three of them we can assess each of them individually:

  - "ref-filter.c:ref_kind_from_refname()" uses it to classify refs.
    It's clear that the intent is to classify based on the ref name,
    only.

  - "refs/reftable_backend.c:reftable_ref_iterator_advance()" uses it to
    filter root refs. Again, using existence checks is pointless here as
    the iterator has just surfaced the ref, so we know it does exist.

  - "refs/files_backend.c:add_pseudoref_and_head_entries()" uses it to
    determine whether it should add a ref to the root directory of its
    iterator. This had the effect that we skipped over any files that
    are either a symbolic ref, or which are not a ref at all.

    The new behaviour is to include symbolic refs know, which aligns us
    with the adapted terminology. Furthermore, files which look like
    root refs but aren't are now mark those as "broken". As broken refs
    are not surfaced by our tooling, this should not lead to a change in
    user-visible behaviour, but may cause us to emit warnings. This
    feels like the right thing to do as we would otherwise just silently
    ignore corrupted root refs completely.

So in all cases the existence check was either superfluous, not in line
with the adapted terminology or masked potential issues. This commit
thus changes the behaviour as proposed and drops the existence check
altogether.

Add a test that verifies that this does not change user-visible
behaviour. Namely, we still don't want to show broken refs to the user
by default in git-for-each-ref(1). What this does allow though is for
internal callers to surface dangling root refs when they pass in the
`DO_FOR_EACH_INCLUDE_BROKEN` flag.

Signed-off-by: Patrick Steinhardt <ps@pks.im>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
2024-05-15 07:30:52 -07:00
Patrick Steinhardt f6936e62a5 refs: rename is_pseudoref() to is_root_ref()
Rename `is_pseudoref()` to `is_root_ref()` to adapt to the newly defined
terminology in our gitglossary(7).

Signed-off-by: Patrick Steinhardt <ps@pks.im>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
2024-05-15 07:30:51 -07:00
Patrick Steinhardt c8f815c208 refs: remove functions without ref store
The preceding commit has rewritten all callers of ref-related functions
to use the equivalents that accept a `struct ref_store`. Consequently,
the respective variants without the ref store are now unused. Remove
them.

There are likely patch series in-flight that use the now-removed
functions. To help the authors, the old implementations have been added
to "refs.c" in an ifdef'd section as a reference for how to migrate each
of the respective callers.

Signed-off-by: Patrick Steinhardt <ps@pks.im>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
2024-05-07 10:06:59 -07:00
Patrick Steinhardt 54876c6dfb refs: add exclude_patterns parameter to for_each_fullref_in()
The `for_each_fullref_in()` function is supposedly the ref-store-less
equivalent of `refs_for_each_fullref_in()`, but the latter has gained a
new parameter `exclude_patterns` over time. Bring these two functions
back in sync again by adding the parameter to the former function, as
well.

Signed-off-by: Patrick Steinhardt <ps@pks.im>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
2024-05-07 10:06:59 -07:00
Patrick Steinhardt 39a9ef8fc4 refs: introduce missing functions that accept a struct ref_store
While most of the functions in "refs.h" have a variant that accepts a
`struct ref_store`, some don't. Callers of these functions are thus
forced to implicitly rely on `the_repository` to figure out the ref
store that is to be used.

Introduce those missing functions to address this shortcoming.

Signed-off-by: Patrick Steinhardt <ps@pks.im>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
2024-05-07 10:06:58 -07:00
Karthik Nayak f151dfe3c9 refs: rename refs_create_symref() to refs_update_symref()
The `refs_create_symref()` function is used to update/create a symref.
But it doesn't check the old target of the symref, if existing. It force
updates the symref. In this regard, the name `refs_create_symref()` is a
bit misleading. So let's rename it to `refs_update_symref()`. This is
akin to how 'git-update-ref(1)' also allows us to create apart from
update.

While we're here, rename the arguments in the function to clarify what
they actually signify and reduce confusion.

Signed-off-by: Karthik Nayak <karthik.188@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
2024-05-07 08:51:50 -07:00
Karthik Nayak 1bc4cc3fc4 refs: accept symref values in ref_transaction_update()
The function `ref_transaction_update()` obtains ref information and
flags to create a `ref_update` and add them to the transaction at hand.

To extend symref support in transactions, we need to also accept the
old and new ref targets and process it. This commit adds the required
parameters to the function and modifies all call sites.

The two parameters added are `new_target` and `old_target`. The
`new_target` is used to denote what the reference should point to when
the transaction is applied. Some functions allow this parameter to be
NULL, meaning that the reference is not changed.

The `old_target` denotes the value the reference must have before the
update. Some functions allow this parameter to be NULL, meaning that the
old value of the reference is not checked.

We also update the internal function `ref_transaction_add_update()`
similarly to take the two new parameters.

Signed-off-by: Karthik Nayak <karthik.188@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
2024-05-07 08:51:49 -07:00
Patrick Steinhardt f89356db4a refs/reftable: expose auto compaction via new flag
Under normal circumstances, the "reftable" backend will automatically
perform compaction after appending to the stack. It is thus not
necessary and may even be considered wasteful to run git-pack-refs(1) in
"reftable"-backed repositories as it will cause the backend to compact
all tables into a single one. We do exactly that though when running
`git maintenance run --auto` or `git gc --auto`, which gets spawned by
Git after running some specific commands.

The `--auto` mode is typically only executing optimizations as needed.
To do so, we already use several heuristics for the various different
data structures in Git to determine whether to optimize them or not.
We do not use any heuristics for refs though and instead always optimize
them.

Introduce a new `PACK_REFS_AUTO` flag that can be passed to the backend.
When not handled by the backend we will continue to behave the exact
same as we do right now, that is we optimize refs unconditionally. This
is done for the "files" backend for now to retain current behaviour,
even though we may eventually also want to introduce heuristics here.
For the "reftable" backend though we already do have auto-compaction, so
we can easily reuse that logic to implement the new auto-packing flag.

Note that under normal circumstances, this should always end up being a
no-op. After all, we already invoke the code for every single addition
to the stack. But there are special cases where it can still be helpful
to execute the auto-compaction code explicitly:

  - Concurrent writers may cause compaction to not run due to locks.

  - Callers may decide to disable compaction altogether and then pack
    refs at a later point due to various reasons.

  - Other implementations of the reftable format may do compaction
    differently or even not at all.

Signed-off-by: Patrick Steinhardt <ps@pks.im>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
2024-03-25 09:54:07 -07:00
Patrick Steinhardt 35aeabd6c2 refs: remove PACK_REFS_ALL flag
The intent of the `PACK_REFS_ALL` flag is to ask the backend to compact
all refs instead of only a subset of them. Thus, this flag gets passed
down to `refs_pack_refs()` via `struct pack_refs_opts::flags`.

But starting with 4fe42f326e (pack-refs: teach pack-refs --include
option, 2023-05-12), the flag's semantics have changed. Instead of being
handled by the respective backends, this flag is now getting handled by
the callers of `refs_pack_refs()` which will add a single glob ("*") to
the list of refs-to-be-packed. Thus, the flag serves no purpose to the
ref backends anymore.

Remove the flag and replace it with a local variable.

Signed-off-by: Patrick Steinhardt <ps@pks.im>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
2024-03-25 09:54:07 -07:00
Patrick Steinhardt 0f65c7a676 refs: move struct pack_refs_opts to where it's used
The declaration of `struct pack_refs_opts` is in a seemingly random
place. Move it so that it's located right next to its flags and
functions that use it.

Signed-off-by: Patrick Steinhardt <ps@pks.im>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
2024-03-25 09:54:07 -07:00
Junio C Hamano d037212d97 Merge branch 'kn/for-all-refs'
"git for-each-ref" learned "--include-root-refs" option to show
even the stuff outside the 'refs/' hierarchy.

* kn/for-all-refs:
  for-each-ref: add new option to include root refs
  ref-filter: rename 'FILTER_REFS_ALL' to 'FILTER_REFS_REGULAR'
  refs: introduce `refs_for_each_include_root_refs()`
  refs: extract out `loose_fill_ref_dir_regular_file()`
  refs: introduce `is_pseudoref()` and `is_headref()`
2024-03-05 09:44:44 -08:00
Junio C Hamano 74522bbd98 Merge branch 'jk/reflog-special-cases-fix'
The logic to access reflog entries by date and number had ugly
corner cases at the boundaries, which have been cleaned up.

* jk/reflog-special-cases-fix:
  read_ref_at(): special-case ref@{0} for an empty reflog
  get_oid_basic(): special-case ref@{n} for oldest reflog entry
  Revert "refs: allow @{n} to work with n-sized reflog"
2024-03-05 09:44:42 -08:00
Jeff King 5edd126720 read_ref_at(): special-case ref@{0} for an empty reflog
The previous commit special-cased get_oid_basic()'s handling of ref@{n}
for a reflog with n entries. But its special case doesn't work for
ref@{0} in an empty reflog, because read_ref_at() dies when it notices
the empty reflog!

We can make this work by special-casing this in read_ref_at(). It's
somewhat gross, for two reasons:

  1. We have no reflog entry to describe in the "msg" out-parameter. So
     we have to leave it uninitialized or make something up.

  2. Likewise, we have no oid to put in the "oid" out-parameter. Leaving
     it untouched is actually the best thing here, as all of the callers
     will have initialized it with the current ref value via
     repo_dwim_log(). This is rather subtle, but it is how things worked
     in 6436a20284 (refs: allow @{n} to work with n-sized reflog,
     2021-01-07) before we reverted it.

The key difference from 6436a20284 here is that we'll return "1" to
indicate that we _didn't_ find the requested reflog entry. Coupled with
the special-casing in get_oid_basic() in the previous commit, that's
enough to make looking up ref@{0} work, and we can flip 6436a20284's
test back to expect_success.

It also means that the call in show-branch which segfaulted with
6436a20284 (and which is now tested in t3202) remains OK. The caller
notices that we could not find any reflog entry, and so it breaks out of
its loop, showing nothing. This is different from the current behavior
of producing an error, but it's just as reasonable (and is exactly what
we'd do if you asked it to walk starting at ref@{1} but there was only 1
entry).

Thus nobody should actually look at the reflog entry info we return. But
we'll still put in some fake values just to be on the safe side, since
this is such a subtle and confusing interface. Likewise, we'll document
what's going on in a comment above the function declaration. If this
were a function with a lot of callers, the footgun would probably not be
worth it. But it has only ever had two callers in its 18-year existence,
and it seems unlikely to grow more. So let's hold our noses and let
users enjoy the convenience of a simulated ref@{0}.

Signed-off-by: Jeff King <peff@peff.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
2024-02-26 10:05:35 -08:00
Karthik Nayak d0f00c1ac1 refs: introduce refs_for_each_include_root_refs()
Introduce a new ref iteration flag `DO_FOR_EACH_INCLUDE_ROOT_REFS`,
which will be used to iterate over regular refs plus pseudorefs and
HEAD.

Refs which fall outside the `refs/` and aren't either pseudorefs or HEAD
are more of a grey area. This is because we don't block the users from
creating such refs but they are not officially supported.

Introduce `refs_for_each_include_root_refs()` which calls
`do_for_each_ref()` with this newly introduced flag.

In `refs/files-backend.c`, introduce a new function
`add_pseudoref_and_head_entries()` to add pseudorefs and HEAD to the
`ref_dir`. We then finally call `add_pseudoref_and_head_entries()`
whenever the `DO_FOR_EACH_INCLUDE_ROOT_REFS` flag is set. Any new ref
backend will also have to implement similar changes on its end.

Signed-off-by: Karthik Nayak <karthik.188@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
2024-02-23 10:36:27 -08:00
Karthik Nayak 1eba2240f8 refs: introduce is_pseudoref() and is_headref()
Introduce two new functions `is_pseudoref()` and `is_headref()`. This
provides the necessary functionality for us to add pseudorefs and HEAD
to the loose ref cache in the files backend, allowing us to build
tooling to print these refs.

The `is_pseudoref()` function internally calls `is_pseudoref_syntax()`
but adds onto it by also checking to ensure that the pseudoref either
ends with a "_HEAD" suffix or matches a list of exceptions. After which
we also parse the contents of the pseudoref to ensure that it conforms
to the ref format.

We cannot directly add the new syntax checks to `is_pseudoref_syntax()`
because the function is also used by `is_current_worktree_ref()` and
making it stricter to match only known pseudorefs might have unintended
consequences due to files like 'BISECT_START' which isn't a pseudoref
but sometimes contains object ID.

Keeping this in mind, we leave `is_pseudoref_syntax()` as is and create
`is_pseudoref()` which is stricter. Ideally we'd want to move the new
syntax checks to `is_pseudoref_syntax()` but a prerequisite for this
would be to actually remove the exception list by converting those
pseudorefs to also contain a '_HEAD' suffix and perhaps move bisect
related files like 'BISECT_START' to a new directory similar to the
'rebase-merge' directory.

Helped-by: Jeff King <peff@peff.net>
Signed-off-by: Karthik Nayak <karthik.188@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
2024-02-23 10:36:27 -08:00
Patrick Steinhardt 31f898397b refs: drop unused params from the reflog iterator callback
The ref and reflog iterators share much of the same underlying code to
iterate over the corresponding entries. This results in some weird code
because the reflog iterator also exposes an object ID as well as a flag
to the callback function. Neither of these fields do refer to the reflog
though -- they refer to the corresponding ref with the same name. This
is quite misleading. In practice at least the object ID cannot really be
implemented in any other way as a reflog does not have a specific object
ID in the first place. This is further stressed by the fact that none of
the callbacks except for our test helper make use of these fields.

Split up the infrastucture so that ref and reflog iterators use separate
callback signatures. This allows us to drop the nonsensical fields from
the reflog iterator.

Note that internally, the backends still use the same shared infra to
iterate over both types. As the backends should never end up being
called directly anyway, this is not much of a problem and thus kept
as-is for simplicity's sake.

Signed-off-by: Patrick Steinhardt <ps@pks.im>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
2024-02-21 09:58:06 -08:00
Junio C Hamano dc8ce995a2 Merge branch 'ps/worktree-refdb-initialization'
Instead of manually creating refs/ hierarchy on disk upon a
creation of a secondary worktree, which is only usable via the
files backend, use the refs API to populate it.

* ps/worktree-refdb-initialization:
  builtin/worktree: create refdb via ref backend
  worktree: expose interface to look up worktree by name
  builtin/worktree: move setup of commondir file earlier
  refs/files: skip creation of "refs/{heads,tags}" for worktrees
  setup: move creation of "refs/" into the files backend
  refs: prepare `refs_init_db()` for initializing worktree refs
2024-01-26 08:54:46 -08:00
Junio C Hamano 32c6fc3e30 Merge branch 'ps/refstorage-extension'
Introduce a new extension "refstorage" so that we can mark a
repository that uses a non-default ref backend, like reftable.

* ps/refstorage-extension:
  t9500: write "extensions.refstorage" into config
  builtin/clone: introduce `--ref-format=` value flag
  builtin/init: introduce `--ref-format=` value flag
  builtin/rev-parse: introduce `--show-ref-format` flag
  t: introduce GIT_TEST_DEFAULT_REF_FORMAT envvar
  setup: introduce GIT_DEFAULT_REF_FORMAT envvar
  setup: introduce "extensions.refStorage" extension
  setup: set repository's formats on init
  setup: start tracking ref storage format
  refs: refactor logic to look up storage backends
  worktree: skip reading HEAD when repairing worktrees
  t: introduce DEFAULT_REPO_FORMAT prereq
2024-01-16 10:11:57 -08:00
Patrick Steinhardt 2eb1d0c452 refs/files: skip creation of "refs/{heads,tags}" for worktrees
The files ref backend will create both "refs/heads" and "refs/tags" in
the Git directory. While this logic makes sense for normal repositories,
it does not for worktrees because those refs are "common" refs that
would always be contained in the main repository's ref database.

Introduce a new flag telling the backend that it is expected to create a
per-worktree ref database and skip creation of these dirs in the files
backend when the flag is set. No other backends (currently) need
worktree-specific logic, so this is the only required change to start
creating per-worktree ref databases via `refs_init_db()`.

Signed-off-by: Patrick Steinhardt <ps@pks.im>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
2024-01-08 13:17:30 -08:00
Patrick Steinhardt 2e573d61ff refs: prepare refs_init_db() for initializing worktree refs
The purpose of `refs_init_db()` is to initialize the on-disk files of a
new ref database. The function is quite inflexible right now though, as
callers can neither specify the `struct ref_store` nor can they pass any
flags.

Refactor the interface to accept both of these. This will be required so
that we can start initializing per-worktree ref databases via the ref
backend instead of open-coding the initialization in "worktree.c".

Signed-off-by: Patrick Steinhardt <ps@pks.im>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
2024-01-08 13:17:30 -08:00
Patrick Steinhardt 0fcc285c5e refs: refactor logic to look up storage backends
In order to look up ref storage backends, we're currently using a linked
list of backends, where each backend is expected to set up its `next`
pointer to the next ref storage backend. This is kind of a weird setup
as backends need to be aware of other backends without much of a reason.

Refactor the code so that the array of backends is centrally defined in
"refs.c", where each backend is now identified by an integer constant.
Expose functions to translate from those integer constants to the name
and vice versa, which will be required by subsequent patches.

Signed-off-by: Patrick Steinhardt <ps@pks.im>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
2024-01-02 09:24:47 -08:00
Junio C Hamano 7122f4f747 refs.h: HEAD is not that special
In-code comment explains pseudorefs but used a wrong nomenclature
"special ref".

Signed-off-by: Junio C Hamano <gitster@pobox.com>
2023-12-15 14:08:28 -08:00
Junio C Hamano 39fe402d67 Merge branch 'tb/refs-exclusion-and-packed-refs'
Enumerating refs in the packed-refs file, while excluding refs that
match certain patterns, has been optimized.

* tb/refs-exclusion-and-packed-refs:
  ls-refs.c: avoid enumerating hidden refs where possible
  upload-pack.c: avoid enumerating hidden refs where possible
  builtin/receive-pack.c: avoid enumerating hidden references
  refs.h: implement `hidden_refs_to_excludes()`
  refs.h: let `for_each_namespaced_ref()` take excluded patterns
  revision.h: store hidden refs in a `strvec`
  refs/packed-backend.c: add trace2 counters for jump list
  refs/packed-backend.c: implement jump lists to avoid excluded pattern(s)
  refs/packed-backend.c: refactor `find_reference_location()`
  refs: plumb `exclude_patterns` argument throughout
  builtin/for-each-ref.c: add `--exclude` option
  ref-filter.c: parameterize match functions over patterns
  ref-filter: add `ref_filter_clear()`
  ref-filter: clear reachable list pointers after freeing
  ref-filter.h: provide `REF_FILTER_INIT`
  refs.c: rename `ref_filter`
2023-07-21 13:47:26 -07:00
Taylor Blau 15af64dcfd refs.h: implement hidden_refs_to_excludes()
In subsequent commits, we'll teach `receive-pack` and `upload-pack` to
use the new jump list feature in the packed-refs iterator by ignoring
references which are mentioned via its respective hideRefs lists.

However, the packed-ref jump lists cannot handle un-hiding rules (that
begin with '!'), or namespace comparisons (that begin with '^'). Add a
convenience function to the refs.h API to detect when either of these
conditions are met, and returns an appropriate value to pass as excluded
patterns.

Suggested-by: Jeff King <peff@peff.net>
Signed-off-by: Taylor Blau <me@ttaylorr.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
2023-07-10 14:48:56 -07:00
Taylor Blau e6bf24d39a refs.h: let for_each_namespaced_ref() take excluded patterns
A future commit will want to call `for_each_namespaced_ref()` with
a list of excluded patterns.

We could introduce a variant of that function, say,
`for_each_namespaced_ref_exclude()` which takes the extra parameter, and
reimplement the original function in terms of that. But all but one
caller (in `http-backend.c`) will supply the new parameter, so add the
new parameter to `for_each_namespaced_ref()` itself instead of
introducing a new function.

For now, supply NULL for the list of excluded patterns at all callers to
avoid changing behavior, which we will do in a future change.

Signed-off-by: Taylor Blau <me@ttaylorr.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
2023-07-10 14:48:56 -07:00
Taylor Blau c45841fff8 revision.h: store hidden refs in a strvec
In subsequent commits, it will be convenient to have a 'const char **'
of hidden refs (matching `transfer.hiderefs`, `uploadpack.hideRefs`,
etc.), instead of a `string_list`.

Convert spots throughout the tree that store the list of hidden refs
from a `string_list` to a `strvec`.

Note that in `parse_hide_refs_config()` there is an ugly const-cast used
to avoid an extra copy of each value before trimming any trailing slash
characters. This could instead be written as:

    ref = xstrdup(value);
    len = strlen(ref);
    while (len && ref[len - 1] == '/')
            ref[--len] = '\0';
    strvec_push(hide_refs, ref);
    free(ref);

but the double-copy (once when calling `xstrdup()`, and another via
`strvec_push()`) is wasteful.

Signed-off-by: Taylor Blau <me@ttaylorr.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
2023-07-10 14:48:56 -07:00
Taylor Blau 59c35fac54 refs/packed-backend.c: implement jump lists to avoid excluded pattern(s)
When iterating through the `packed-refs` file in order to answer a query
like:

    $ git for-each-ref --exclude=refs/__hidden__

it would be useful to avoid walking over all of the entries in
`refs/__hidden__/*` when possible, since we know that the ref-filter
code is going to throw them away anyways.

In certain circumstances, doing so is possible. The algorithm for doing
so is as follows:

  - For each excluded pattern, find the first record that matches it,
    and the first record that *doesn't* match it (i.e. the location
    you'd next want to consider when excluding that pattern).

  - Sort the set of excluded regions from the previous step in ascending
    order of the first location within the `packed-refs` file that
    matches.

  - Clean up the results from the previous step: discard empty regions,
    and combine adjacent regions. The set of regions which remains is
    referred to as the "jump list", and never contains any references
    which should be included in the result set.

Then when iterating through the `packed-refs` file, if `iter->pos` is
ever contained in one of the regions from the previous steps, advance
`iter->pos` past the end of that region, and continue enumeration.

Note that we only perform this optimization when none of the excluded
pattern(s) have special meta-characters in them. For a pattern like
"refs/foo[ac]", the excluded regions ("refs/fooa", "refs/fooc", and
everything underneath them) are not connected. A future implementation
that handles this case may split the character class (pretending as if
two patterns were excluded: "refs/fooa", and "refs/fooc").

There are a few other gotchas worth considering. First, note that the
jump list is sorted, so once we jump past a region, we can avoid
considering it (or any regions preceding it) again. The member
`jump_pos` is used to track the first next-possible region to jump
through.

Second, note that the jump list is best-effort, since we do not handle
loose references, and because of the meta-character issue above. The
jump list may not skip past all references which won't appear in the
results, but will never skip over a reference which does appear in the
result set.

In repositories with a large number of hidden references, the speed-up
can be significant. Tests here are done with a copy of linux.git with a
reference "refs/pull/N" pointing at every commit, as in:

    $ git rev-list HEAD | awk '{ print "create refs/pull/" NR " " $0 }' |
        git update-ref --stdin
    $ git pack-refs --all

, it is significantly faster to have `for-each-ref` jump over the
excluded references, as opposed to filtering them out after the fact:

    $ hyperfine \
      'git for-each-ref --format="%(objectname) %(refname)" | grep -vE "^[0-9a-f]{40} refs/pull/"' \
      'git.prev for-each-ref --format="%(objectname) %(refname)" --exclude="refs/pull"' \
      'git.compile for-each-ref --format="%(objectname) %(refname)" --exclude="refs/pull"'
    Benchmark 1: git for-each-ref --format="%(objectname) %(refname)" | grep -vE "^[0-9a-f]{40} refs/pull/"
      Time (mean ± σ):     798.1 ms ±   3.3 ms    [User: 687.6 ms, System: 146.4 ms]
      Range (min … max):   794.5 ms … 805.5 ms    10 runs

    Benchmark 2: git.prev for-each-ref --format="%(objectname) %(refname)" --exclude="refs/pull"
      Time (mean ± σ):      98.9 ms ±   1.4 ms    [User: 93.1 ms, System: 5.7 ms]
      Range (min … max):    97.0 ms … 104.0 ms    29 runs

    Benchmark 3: git.compile for-each-ref --format="%(objectname) %(refname)" --exclude="refs/pull"
      Time (mean ± σ):       4.5 ms ±   0.2 ms    [User: 0.7 ms, System: 3.8 ms]
      Range (min … max):     4.1 ms …   5.8 ms    524 runs

    Summary
      'git.compile for-each-ref --format="%(objectname) %(refname)" --exclude="refs/pull"' ran
       21.87 ± 1.05 times faster than 'git.prev for-each-ref --format="%(objectname) %(refname)" --exclude="refs/pull"'
      176.52 ± 8.19 times faster than 'git for-each-ref --format="%(objectname) %(refname)" | grep -vE "^[0-9a-f]{40} refs/pull/"'

(Comparing stock git and this patch isn't quite fair, since an earlier
commit in this series adds a naive implementation of the `--exclude`
option. `git.prev` is built from the previous commit and includes this
naive implementation).

Using the jump list is fairly straightforward (see the changes to
`refs/packed-backend.c::next_record()`), but constructing the list is
not. To ensure that the construction is correct, add a new suite of
tests in t1419 covering various corner cases (overlapping regions,
partially overlapping regions, adjacent regions, etc.).

Co-authored-by: Jeff King <peff@peff.net>
Signed-off-by: Jeff King <peff@peff.net>
Signed-off-by: Taylor Blau <me@ttaylorr.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
2023-07-10 14:48:55 -07:00
Taylor Blau b269ac53c0 refs: plumb exclude_patterns argument throughout
The subsequent patch will want to access an optional `excluded_patterns`
array within `refs/packed-backend.c` that will cull out certain
references matching any of the given patterns on a best-effort basis.

To do so, the refs subsystem needs to be updated to pass this value
across a number of different locations.

Prepare for a future patch by introducing this plumbing now, passing
NULLs at top-level APIs in order to make that patch less noisy and more
easily readable.

Signed-off-by: Taylor Blau <me@ttaylorr.co>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
2023-07-10 14:48:55 -07:00
John Cai 4fe42f326e pack-refs: teach pack-refs --include option
Allow users to be more selective over which refs to pack by adding an
--include option to git-pack-refs.

The existing options allow some measure of selectivity. By default
git-pack-refs packs all tags. --all can be used to include all refs,
and the previous commit added the ability to exclude certain refs with
--exclude.

While these knobs give the user some selection over which refs to pack,
it could be useful to give more control. For instance, a repository may
have a set of branches that are rarely updated and would benefit from
being packed. --include would allow the user to easily include a set of
branches to be packed while leaving everything else unpacked.

Signed-off-by: John Cai <johncai86@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
2023-05-12 14:54:14 -07:00
John Cai 826ae79fca pack-refs: teach --exclude option to exclude refs from being packed
At GitLab, we have a system that creates ephemeral internal refs that
don't live long before getting deleted. Having an option to exclude
certain refs from a packed-refs file allows these internal references to
be deleted much more efficiently.

Add an --exclude option to the pack-refs builtin, and use the ref
exclusions API to exclude certain refs from being packed into the final
packed-refs file

Signed-off-by: John Cai <johncai86@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
2023-05-12 14:54:14 -07:00
Junio C Hamano 6047b28eb7 Merge branch 'en/header-split-cleanup'
Split key function and data structure definitions out of cache.h to
new header files and adjust the users.

* en/header-split-cleanup:
  csum-file.h: remove unnecessary inclusion of cache.h
  write-or-die.h: move declarations for write-or-die.c functions from cache.h
  treewide: remove cache.h inclusion due to setup.h changes
  setup.h: move declarations for setup.c functions from cache.h
  treewide: remove cache.h inclusion due to environment.h changes
  environment.h: move declarations for environment.c functions from cache.h
  treewide: remove unnecessary includes of cache.h
  wrapper.h: move declarations for wrapper.c functions from cache.h
  path.h: move function declarations for path.c functions from cache.h
  cache.h: remove expand_user_path()
  abspath.h: move absolute path functions from cache.h
  environment: move comment_line_char from cache.h
  treewide: remove unnecessary cache.h inclusion from several sources
  treewide: remove unnecessary inclusion of gettext.h
  treewide: be explicit about dependence on gettext.h
  treewide: remove unnecessary cache.h inclusion from a few headers
2023-04-06 13:38:31 -07:00
Ævar Arnfjörð Bjarmason 12cb1c10a6 cocci: apply the "refs.h" part of "the_repository.pending"
Apply the part of "the_repository.pending.cocci" pertaining to
"refs.h".

Signed-off-by: Ævar Arnfjörð Bjarmason <avarab@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
2023-03-28 07:36:46 -07:00
Elijah Newren a6dc3d364c treewide: remove unnecessary cache.h inclusion from a few headers
Ever since a64215b6cd ("object.h: stop depending on cache.h; make
cache.h depend on object.h", 2023-02-24), we have a few headers that
could have replaced their include of cache.h with an include of
object.h.  Make that change now.

Some C files had to start including cache.h after this change (or some
smaller header it had brought in), because the C files were depending
on things from cache.h but were only formerly implicitly getting
cache.h through one of these headers being modified in this patch.

Signed-off-by: Elijah Newren <newren@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
2023-03-21 10:56:50 -07:00
Jeff King 91e2ab1587 ls-refs: use repository parameter to iterate refs
The ls_refs() function (for the v2 protocol command of the same name)
takes a repository parameter (like all v2 commands), but ignores it. It
should use it to access the refs.

This isn't a bug in practice, since we only call this function when
serving upload-pack from the main repository. But it's an awkward
gotcha, and it causes -Wunused-parameter to complain.

The main reason we don't use the repository parameter is that the ref
iteration interface we call doesn't have a "refs_" variant that takes a
ref_store. However we can easily add one. In fact, since there is only
one other caller (in ref-filter.c), there is no need to maintain the
non-repository wrapper; that caller can just use the_repository. It's
still a long way from consistently using a repository object, but it's
one small step in the right direction.

Signed-off-by: Jeff King <peff@peff.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
2022-12-13 22:16:22 +09:00
Patrick Steinhardt 9b67eb6fbe refs: get rid of global list of hidden refs
We're about to add a new argument to git-rev-list(1) that allows it to
add all references that are visible when taking `transfer.hideRefs` et
al into account. This will require us to potentially parse multiple sets
of hidden refs, which is not easily possible right now as there is only
a single, global instance of the list of parsed hidden refs.

Refactor `parse_hide_refs_config()` and `ref_is_hidden()` so that both
take the list of hidden references as input and adjust callers to keep a
local list, instead. This allows us to easily use multiple hidden-ref
lists. Furthermore, it allows us to properly free this list before we
exit.

Signed-off-by: Patrick Steinhardt <ps@pks.im>
Signed-off-by: Taylor Blau <me@ttaylorr.com>
2022-11-17 16:22:51 -05:00
Han-Wen Nienhuys 71e5473493 refs: unify parse_worktree_ref() and ref_type()
The logic to handle worktree refs (worktrees/NAME/REF and
main-worktree/REF) existed in two places:

* ref_type() in refs.c

* parse_worktree_ref() in worktree.c

Collapse this logic together in one function parse_worktree_ref():
this avoids having to cross-check the result of parse_worktree_ref()
and ref_type().

Introduce enum ref_worktree_type, which is slightly different from
enum ref_type. The latter is a misleading name (one would think that
'ref_type' would have the symref option).

Instead, enum ref_worktree_type only makes explicit how a refname
relates to a worktree. From this point of view, HEAD and
refs/bisect/abc are the same: they specify the current worktree
implicitly.

The files-backend must avoid packing refs/bisect/* and friends into
packed-refs, so expose is_per_worktree_ref() separately.

Signed-off-by: Han-Wen Nienhuys <hanwen@google.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
2022-09-19 11:11:11 -07:00
Derrick Stolee b9342b3fd6 refs: add array of ref namespaces
Git interprets different meanings to different refs based on their
names. Some meanings are cosmetic, like how refs in  'refs/remotes/*'
are colored differently from refs in 'refs/heads/*'. Others are more
critical, such as how replace refs are interpreted.

Before making behavior changes based on ref namespaces, collect all
known ref namespaces into a array of ref_namespace_info structs. This
array is indexed by the new ref_namespace enum for quick access.

As of this change, this array is purely documentation. Future changes
will add dependencies on this array.

Signed-off-by: Derrick Stolee <derrickstolee@github.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
2022-08-05 14:13:12 -07:00
Junio C Hamano c6da34a610 Revert "Merge branch 'ps/avoid-unnecessary-hook-invocation-with-packed-refs'"
This reverts commit 991b4d47f0, reversing
changes made to bcd020f88e.
2022-04-13 15:51:33 -07:00
Patrick Steinhardt cd475b3b03 refs: add ability for backends to special-case reading of symbolic refs
Reading of symbolic and non-symbolic references is currently treated the
same in reference backends: we always call `refs_read_raw_ref()` and
then decide based on the returned flags what type it is. This has one
downside though: symbolic references may be treated different from
normal references in a backend from normal references. The packed-refs
backend for example doesn't even know about symbolic references, and as
a result it is pointless to even ask it for one.

There are cases where we really only care about whether a reference is
symbolic or not, but don't care about whether it exists at all or may be
a non-symbolic reference. But it is not possible to optimize for this
case right now, and as a consequence we will always first check for a
loose reference to exist, and if it doesn't, we'll query the packed-refs
backend for a known-to-not-be-symbolic reference. This is inefficient
and requires us to search all packed references even though we know to
not care for the result at all.

Introduce a new function `refs_read_symbolic_ref()` which allows us to
fix this case. This function will only ever return symbolic references
and can thus optimize for the scenario layed out above. By default, if
the backend doesn't provide an implementation for it, we just use the
old code path and fall back to `read_raw_ref()`. But in case the backend
provides its own, more efficient implementation, we will use that one
instead.

Note that this function is explicitly designed to not distinguish
between missing references and non-symbolic references. If it did, we'd
be forced to always search the packed-refs backend to see whether the
symbolic reference the user asked for really doesn't exist, or if it
exists as a non-symbolic reference.

Signed-off-by: Patrick Steinhardt <ps@pks.im>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
2022-03-01 10:13:46 -08:00
Junio C Hamano 34363403a2 Merge branch 'ps/fetch-atomic' into ps/fetch-mirror-optim
* ps/fetch-atomic:
  fetch: make `--atomic` flag cover pruning of refs
  fetch: make `--atomic` flag cover backfilling of tags
  refs: add interface to iterate over queued transactional updates
  fetch: report errors when backfilling tags fails
  fetch: control lifecycle of FETCH_HEAD in a single place
  fetch: backfill tags before setting upstream
  fetch: increase test coverage of fetches
2022-03-01 10:11:00 -08:00
Junio C Hamano 991b4d47f0 Merge branch 'ps/avoid-unnecessary-hook-invocation-with-packed-refs'
Because a deletion of ref would need to remove it from both the
loose ref store and the packed ref store, a delete-ref operation
that logically removes one ref may end up invoking ref-transaction
hook twice, which has been corrected.

* ps/avoid-unnecessary-hook-invocation-with-packed-refs:
  refs: skip hooks when deleting uncovered packed refs
  refs: do not execute reference-transaction hook on packing refs
  refs: demonstrate excessive execution of the reference-transaction hook
  refs: allow skipping the reference-transaction hook
  refs: allow passing flags when beginning transactions
  refs: extract packed_refs_delete_refs() to allow control of transaction
2022-02-18 13:53:27 -08:00
Patrick Steinhardt 4f2ba2d06a refs: add interface to iterate over queued transactional updates
There is no way for a caller to see whether a reference update has
already been queued up for a given reference transaction. There are
multiple alternatives to provide this functionality:

    - We may add a function that simply tells us whether a specific
      reference has already been queued. If implemented naively then
      this would potentially be quadratic in runtime behaviour if this
      question is asked repeatedly because we have to iterate over all
      references every time. The alternative would be to add a hashmap
      of all queued reference updates to speed up the lookup, but this
      adds overhead to all callers.

    - We may add a flag to `ref_transaction_add_update()` that causes it
      to skip duplicates, but this has the same runtime concerns as the
      first alternative.

    - We may add an interface which lets callers collect all updates
      which have already been queued such that he can avoid re-adding
      them. This is the most flexible approach and puts the burden on
      the caller, but also allows us to not impact any of the existing
      callsites which don't need this information.

This commit implements the last approach: it allows us to compute the
map of already-queued updates once up front such that we can then skip
all subsequent references which are already part of this map.

Signed-off-by: Patrick Steinhardt <ps@pks.im>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
2022-02-17 11:19:44 -08:00
Ævar Arnfjörð Bjarmason ce14de03db refs API: remove "failure_errno" from refs_resolve_ref_unsafe()
Remove the now-unused "failure_errno" parameter from the
refs_resolve_ref_unsafe() signature. In my recent 96f6623ada (Merge
branch 'ab/refs-errno-cleanup', 2021-11-29) series we made all of its
callers explicitly request the errno via an output parameter.

As that series shows all but one caller ended up passing in a
boilerplate "ignore_errno", since they only cared about whether the
return value was NULL or not, i.e. if the ref could be resolved.

There was one small issue with that series fixed with a follow-up in
31e3912369 (Merge branch 'ab/refs-errno-cleanup', 2022-01-14) a small
bug in that series was fixed.

After those two there was one caller left in sequencer.c that used the
"failure_errno', but as of the preceding commit it uses a boilerplate
"ignore_errno" instead.

This leaves the public refs API without any use of "failure_errno" at
all. We could still do with a bit of cleanup and generalization
between refs.c and refs/files-backend.c before the "reftable"
integration lands, but that's all internal to the reference code
itself.

So let's remove this output parameter. Not only isn't it used now, but
it's unlikely that we'll want it again in the future. We'd like to
slowly move the refs API to a more file-backend independent way of
communicating error codes, having it use a "failure_errno" was only
the first step in that direction. If this or any other function needs
to communicate what specifically is wrong with the requested "refname"
it'll be better to have the function set some output enum of
well-defined error states than piggy-backend on "errno".

Signed-off-by: Ævar Arnfjörð Bjarmason <avarab@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
2022-01-26 15:58:41 -08:00
Patrick Steinhardt 958fbc74e3 refs: allow skipping the reference-transaction hook
The reference-transaction hook is executing whenever we prepare, commit
or abort a reference transaction. While this is mostly intentional, in
case of the files backend we're leaking the implementation detail that
the store is in fact a composite store with one loose and one packed
backend to the caller. So while we want to execute the hook for all
logical updates, executing it for such implementation details is
unexpected.

Prepare for a fix by adding a new flag which allows to skip execution of
the hook.

Signed-off-by: Patrick Steinhardt <ps@pks.im>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
2022-01-17 11:01:45 -08:00
Patrick Steinhardt fbe73f61cb refs: allow passing flags when beginning transactions
We do not currently have any flags when creating reference transactions,
but we'll add one to disable execution of the reference transaction hook
in some cases.

Allow passing flags to `ref_store_transaction_begin()` to prepare for
this change.

Signed-off-by: Patrick Steinhardt <ps@pks.im>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
2022-01-17 11:01:44 -08:00