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* refs: add referent to each_ref_fnJohn Cai2024-08-091-1/+1
| | | | | | | | | Add a parameter to each_ref_fn so that callers to the ref APIs that use this function as a callback can have acess to the unresolved value of a symbolic ref. Signed-off-by: John Cai <johncai86@gmail.com> Signed-off-by: Junio C Hamano <gitster@pobox.com>
* global: introduce `USE_THE_REPOSITORY_VARIABLE` macroPatrick Steinhardt2024-06-141-0/+2
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | Use of the `the_repository` variable is deprecated nowadays, and we slowly but steadily convert the codebase to not use it anymore. Instead, callers should be passing down the repository to work on via parameters. It is hard though to prove that a given code unit does not use this variable anymore. The most trivial case, merely demonstrating that there is no direct use of `the_repository`, is already a bit of a pain during code reviews as the reviewer needs to manually verify claims made by the patch author. The bigger problem though is that we have many interfaces that implicitly rely on `the_repository`. Introduce a new `USE_THE_REPOSITORY_VARIABLE` macro that allows code units to opt into usage of `the_repository`. The intent of this macro is to demonstrate that a certain code unit does not use this variable anymore, and to keep it from new dependencies on it in future changes, be it explicit or implicit For now, the macro only guards `the_repository` itself as well as `the_hash_algo`. There are many more known interfaces where we have an implicit dependency on `the_repository`, but those are not guarded at the current point in time. Over time though, we should start to add guards as required (or even better, just remove them). Define the macro as required in our code units. As expected, most of our code still relies on the global variable. Nearly all of our builtins rely on the variable as there is no way yet to pass `the_repository` to their entry point. For now, declare the macro in "biultin.h" to keep the required changes at least a little bit more contained. Signed-off-by: Patrick Steinhardt <ps@pks.im> Signed-off-by: Junio C Hamano <gitster@pobox.com>
* config: clarify memory ownership in `git_config_string()`Patrick Steinhardt2024-05-271-1/+1
| | | | | | | | | | The out parameter of `git_config_string()` is a `const char **` even though we transfer ownership of memory to the caller. This is quite misleading and has led to many memory leaks all over the place. Adapt the parameter to instead be `char **`. Signed-off-by: Patrick Steinhardt <ps@pks.im> Signed-off-by: Junio C Hamano <gitster@pobox.com>
* cocci: apply rules to rewrite callers of "refs" interfacesPatrick Steinhardt2024-05-071-1/+2
| | | | | | | | | Apply the rules that rewrite callers of "refs" interfaces to explicitly pass `struct ref_store`. The resulting patch has been applied with the `--whitespace=fix` option. Signed-off-by: Patrick Steinhardt <ps@pks.im> Signed-off-by: Junio C Hamano <gitster@pobox.com>
* Merge branch 'eb/hash-transition'Junio C Hamano2024-03-281-1/+1
|\ | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | Work to support a repository that work with both SHA-1 and SHA-256 hash algorithms has started. * eb/hash-transition: (30 commits) t1016-compatObjectFormat: add tests to verify the conversion between objects t1006: test oid compatibility with cat-file t1006: rename sha1 to oid test-lib: compute the compatibility hash so tests may use it builtin/ls-tree: let the oid determine the output algorithm object-file: handle compat objects in check_object_signature tree-walk: init_tree_desc take an oid to get the hash algorithm builtin/cat-file: let the oid determine the output algorithm rev-parse: add an --output-object-format parameter repository: implement extensions.compatObjectFormat object-file: update object_info_extended to reencode objects object-file-convert: convert commits that embed signed tags object-file-convert: convert commit objects when writing object-file-convert: don't leak when converting tag objects object-file-convert: convert tag objects when writing object-file-convert: add a function to convert trees between algorithms object: factor out parse_mode out of fast-import and tree-walk into in object.h cache: add a function to read an OID of a specific algorithm tag: sign both hashes commit: export add_header_signature to support handling signatures on tags ...
| * tree-walk: init_tree_desc take an oid to get the hash algorithmEric W. Biederman2023-10-021-1/+1
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | To make it possible for git ls-tree to display the tree encoded in the hash algorithm of the oid specified to git ls-tree, update init_tree_desc to take as a parameter the oid of the tree object. Update all callers of init_tree_desc and init_tree_desc_gently to pass the oid of the tree object. Use the oid of the tree object to discover the hash algorithm of the oid and store that hash algorithm in struct tree_desc. Use the hash algorithm in decode_tree_entry and update_tree_entry_internal to handle reading a tree object encoded in a hash algorithm that differs from the repositories hash algorithm. Signed-off-by: "Eric W. Biederman" <ebiederm@xmission.com> Signed-off-by: Junio C Hamano <gitster@pobox.com>
* | treewide: remove unnecessary includes in source filesElijah Newren2023-12-261-5/+0
|/ | | | | | | | | | | | | | | | | | Each of these were checked with gcc -E -I. ${SOURCE_FILE} | grep ${HEADER_FILE} to ensure that removing the direct inclusion of the header actually resulted in that header no longer being included at all (i.e. that no other header pulled it in transitively). ...except for a few cases where we verified that although the header was brought in transitively, nothing from it was directly used in that source file. These cases were: * builtin/credential-cache.c * builtin/pull.c * builtin/send-pack.c Signed-off-by: Elijah Newren <newren@gmail.com> Signed-off-by: Junio C Hamano <gitster@pobox.com>
* Merge branch 'cw/compat-util-header-cleanup'Junio C Hamano2023-07-171-1/+0
|\ | | | | | | | | | | | | | | | | | | | | | | | | Further shuffling of declarations across header files to streamline file dependencies. * cw/compat-util-header-cleanup: git-compat-util: move alloc macros to git-compat-util.h treewide: remove unnecessary includes for wrapper.h kwset: move translation table from ctype sane-ctype.h: create header for sane-ctype macros git-compat-util: move wrapper.c funcs to its header git-compat-util: move strbuf.c funcs to its header
| * git-compat-util: move alloc macros to git-compat-util.hCalvin Wan2023-07-051-1/+0
| | | | | | | | | | | | | | | | | | | | | | alloc_nr, ALLOC_GROW, and ALLOC_GROW_BY are commonly used macros for dynamic array allocation. Moving these macros to git-compat-util.h with the other alloc macros focuses alloc.[ch] to allocation for Git objects and additionally allows us to remove inclusions to alloc.h from files that solely used the above macros. Signed-off-by: Calvin Wan <calvinwan@google.com> Signed-off-by: Junio C Hamano <gitster@pobox.com>
* | config: add ctx arg to config_fn_tGlen Choo2023-06-281-1/+3
|/ | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | Add a new "const struct config_context *ctx" arg to config_fn_t to hold additional information about the config iteration operation. config_context has a "struct key_value_info kvi" member that holds metadata about the config source being read (e.g. what kind of config source it is, the filename, etc). In this series, we're only interested in .kvi, so we could have just used "struct key_value_info" as an arg, but config_context makes it possible to add/adjust members in the future without changing the config_fn_t signature. We could also consider other ways of organizing the args (e.g. moving the config name and value into config_context or key_value_info), but in my experiments, the incremental benefit doesn't justify the added complexity (e.g. a config_fn_t will sometimes invoke another config_fn_t but with a different config value). In subsequent commits, the .kvi member will replace the global "struct config_reader" in config.c, making config iteration a global-free operation. It requires much more work for the machinery to provide meaningful values of .kvi, so for now, merely change the signature and call sites, pass NULL as a placeholder value, and don't rely on the arg in any meaningful way. Most of the changes are performed by contrib/coccinelle/config_fn_ctx.pending.cocci, which, for every config_fn_t: - Modifies the signature to accept "const struct config_context *ctx" - Passes "ctx" to any inner config_fn_t, if needed - Adds UNUSED attributes to "ctx", if needed Most config_fn_t instances are easily identified by seeing if they are called by the various config functions. Most of the remaining ones are manually named in the .cocci patch. Manual cleanups are still needed, but the majority of it is trivial; it's either adjusting config_fn_t that the .cocci patch didn't catch, or adding forward declarations of "struct config_context ctx" to make the signatures make sense. The non-trivial changes are in cases where we are invoking a config_fn_t outside of config machinery, and we now need to decide what value of "ctx" to pass. These cases are: - trace2/tr2_cfg.c:tr2_cfg_set_fl() This is indirectly called by git_config_set() so that the trace2 machinery can notice the new config values and update its settings using the tr2 config parsing function, i.e. tr2_cfg_cb(). - builtin/checkout.c:checkout_main() This calls git_xmerge_config() as a shorthand for parsing a CLI arg. This might be worth refactoring away in the future, since git_xmerge_config() can call git_default_config(), which can do much more than just parsing. Handle them by creating a KVI_INIT macro that initializes "struct key_value_info" to a reasonable default, and use that to construct the "ctx" arg. Signed-off-by: Glen Choo <chooglen@google.com> Signed-off-by: Junio C Hamano <gitster@pobox.com>
* treewide: remove cache.h inclusion due to object.h changesElijah Newren2023-04-111-1/+1
| | | | | | Signed-off-by: Elijah Newren <newren@gmail.com> Acked-by: Calvin Wan <calvinwan@google.com> Signed-off-by: Junio C Hamano <gitster@pobox.com>
* Merge branch 'ab/remove-implicit-use-of-the-repository' into ↵Junio C Hamano2023-04-041-2/+3
|\ | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | en/header-split-cache-h * ab/remove-implicit-use-of-the-repository: libs: use "struct repository *" argument, not "the_repository" post-cocci: adjust comments for recent repo_* migration cocci: apply the "revision.h" part of "the_repository.pending" cocci: apply the "rerere.h" part of "the_repository.pending" cocci: apply the "refs.h" part of "the_repository.pending" cocci: apply the "promisor-remote.h" part of "the_repository.pending" cocci: apply the "packfile.h" part of "the_repository.pending" cocci: apply the "pretty.h" part of "the_repository.pending" cocci: apply the "object-store.h" part of "the_repository.pending" cocci: apply the "diff.h" part of "the_repository.pending" cocci: apply the "commit.h" part of "the_repository.pending" cocci: apply the "commit-reach.h" part of "the_repository.pending" cocci: apply the "cache.h" part of "the_repository.pending" cocci: add missing "the_repository" macros to "pending" cocci: sort "the_repository" rules by header cocci: fix incorrect & verbose "the_repository" rules cocci: remove dead rule from "the_repository.pending.cocci"
| * cocci: apply the "commit.h" part of "the_repository.pending"Ævar Arnfjörð Bjarmason2023-03-281-2/+3
| | | | | | | | | | | | | | | | Apply the part of "the_repository.pending.cocci" pertaining to "commit.h". Signed-off-by: Ævar Arnfjörð Bjarmason <avarab@gmail.com> Signed-off-by: Junio C Hamano <gitster@pobox.com>
* | csum-file.h: remove unnecessary inclusion of cache.hElijah Newren2023-03-211-1/+1
| | | | | | | | | | | | | | | | | | | | | | With the change in the last commit to move several functions to write-or-die.h, csum-file.h no longer needs to include cache.h. However, removing that include forces several other C files, which directly or indirectly dependend upon csum-file.h's inclusion of cache.h, to now be more explicit about their dependencies. Signed-off-by: Elijah Newren <newren@gmail.com> Signed-off-by: Junio C Hamano <gitster@pobox.com>
* | treewide: be explicit about dependence on gettext.hElijah Newren2023-03-211-0/+1
| | | | | | | | | | | | | | | | | | | | | | | | | | | | Dozens of files made use of gettext functions, without explicitly including gettext.h. This made it more difficult to find which files could remove a dependence on cache.h. Make C files explicitly include gettext.h if they are using it. However, while compat/fsmonitor/fsm-ipc-darwin.c should also gain an include of gettext.h, it was left out to avoid conflicting with an in-flight topic. Signed-off-by: Elijah Newren <newren@gmail.com> Signed-off-by: Junio C Hamano <gitster@pobox.com>
* | Merge branch 'en/header-cleanup'Junio C Hamano2023-03-171-1/+3
|\ \ | |/ |/| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | Code clean-up to clarify the rule that "git-compat-util.h" must be the first to be included. * en/header-cleanup: diff.h: remove unnecessary include of object.h Remove unnecessary includes of builtin.h treewide: replace cache.h with more direct headers, where possible replace-object.h: move read_replace_refs declaration from cache.h to here object-store.h: move struct object_info from cache.h dir.h: refactor to no longer need to include cache.h object.h: stop depending on cache.h; make cache.h depend on object.h ident.h: move ident-related declarations out of cache.h pretty.h: move has_non_ascii() declaration from commit.h cache.h: remove dependence on hex.h; make other files include it explicitly hex.h: move some hex-related declarations from cache.h hash.h: move some oid-related declarations from cache.h alloc.h: move ALLOC_GROW() functions from cache.h treewide: remove unnecessary cache.h includes in source files treewide: remove unnecessary cache.h includes treewide: remove unnecessary git-compat-util.h includes in headers treewide: ensure one of the appropriate headers is sourced first
| * cache.h: remove dependence on hex.h; make other files include it explicitlyElijah Newren2023-02-241-0/+1
| | | | | | | | | | Signed-off-by: Elijah Newren <newren@gmail.com> Signed-off-by: Junio C Hamano <gitster@pobox.com>
| * alloc.h: move ALLOC_GROW() functions from cache.hElijah Newren2023-02-241-1/+2
| | | | | | | | | | | | | | | | | | This allows us to replace includes of cache.h with includes of the much smaller alloc.h in many places. It does mean that we also need to add includes of alloc.h in a number of C files. Signed-off-by: Elijah Newren <newren@gmail.com> Signed-off-by: Junio C Hamano <gitster@pobox.com>
* | delta-islands: fix segfault when freeing island marksPatrick Steinhardt2023-02-211-5/+7
|/ | | | | | | | | | | | | | | | | | | In 647982bb71 (delta-islands: free island_marks and bitmaps, 2023-02-03) we have introduced logic to free `island_marks` in order to reduce heap memory usage in git-pack-objects(1). This commit is causing segfaults in the case where this Git command does not load delta islands at all, e.g. when reading object IDs from standard input. One such crash can be hit when using repacking multi-pack-indices with delta islands enabled. The root cause of this bug is that we unconditionally dereference the `island_marks` variable even in the case where it is a `NULL` pointer, which is fixed by making it conditional. Note that we still leave the logic in place to set the pointer to `-1` to detect use-after-free bugs even when there are no loaded island marks at all. Signed-off-by: Patrick Steinhardt <ps@pks.im> Acked-by: Eric Wong <e@80x24.org> Signed-off-by: Junio C Hamano <gitster@pobox.com>
* delta-islands: free island_marks and bitmapsEric Wong2023-02-041-0/+14
| | | | | | | | | | | | | | | On my mirror of linux.git forkgroup with 780 islands, this saves nearly 4G of heap memory in pack-objects. This savings only benefits delta island users of pack bitmaps, as the process would otherwise be exiting anyways. However, there's probably not many delta island users, but the majority of delta island users would also be pack bitmaps users. Signed-off-by: Eric Wong <e@80x24.org> Helped-by: Ævar Arnfjörð Bjarmason <avarab@gmail.com> Helped-by: Jeff King <peff@peff.net> Signed-off-by: Junio C Hamano <gitster@pobox.com>
* delta-islands: free island-related data after useEric Wong2022-11-191-20/+51
| | | | | | | | | | | | | | On my use case involving 771 islands of Linux on kernel.org, this reduces memory usage by around 25MB. The bulk of that comes from free_remote_islands, since free_config_regexes only saves around 40k. This memory is saved early in the memory-intensive pack process, making it available for the remainder of the long process. Signed-off-by: Eric Wong <e@80x24.org> Co-authored-by: Ævar Arnfjörð Bjarmason <avarab@gmail.com> Signed-off-by: Taylor Blau <me@ttaylorr.com>
* git-compat-util.h: use "UNUSED", not "UNUSED(var)"Ævar Arnfjörð Bjarmason2022-09-011-2/+2
| | | | | | | | | | | | | | | | | | | | | | | As reported in [1] the "UNUSED(var)" macro introduced in 2174b8c75de (Merge branch 'jk/unused-annotation' into next, 2022-08-24) breaks coccinelle's parsing of our sources in files where it occurs. Let's instead partially go with the approach suggested in [2] of making this not take an argument. As noted in [1] "coccinelle" will ignore such tokens in argument lists that it doesn't know about, and it's less of a surprise to syntax highlighters. This undoes the "help us notice when a parameter marked as unused is actually use" part of 9b240347543 (git-compat-util: add UNUSED macro, 2022-08-19), a subsequent commit will further tweak the macro to implement a replacement for that functionality. 1. https://lore.kernel.org/git/220825.86ilmg4mil.gmgdl@evledraar.gmail.com/ 2. https://lore.kernel.org/git/220819.868rnk54ju.gmgdl@evledraar.gmail.com/ Signed-off-by: Ævar Arnfjörð Bjarmason <avarab@gmail.com> Signed-off-by: Junio C Hamano <gitster@pobox.com>
* config: mark unused callback parametersJeff King2022-08-191-1/+1
| | | | | | | | | | | | | | The callback passed to git_config() must conform to a particular interface. But most callbacks don't actually look at the extra "void *data" parameter. Let's mark the unused parameters to make -Wunused-parameter happy. Note there's one unusual case here in get_remote_default() where we actually ignore the "value" parameter. That's because it's only checking whether the option is found at all, and not parsing its value. Signed-off-by: Jeff King <peff@peff.net> Signed-off-by: Junio C Hamano <gitster@pobox.com>
* refs: mark unused each_ref_fn parametersJeff King2022-08-191-1/+1
| | | | | | | | | Functions used with for_each_ref(), etc, need to conform to the each_ref_fn interface. But most of them don't need every parameter; let's annotate the unused ones to quiet -Wunused-parameter. Signed-off-by: Jeff King <peff@peff.net> Signed-off-by: Junio C Hamano <gitster@pobox.com>
* oid_array: rename source file from sha1-arrayJeff King2020-03-301-1/+1
| | | | | | | | | | | | | | | | | | | | | | We renamed the actual data structure in 910650d2f8 (Rename sha1_array to oid_array, 2017-03-31), but the file is still called sha1-array. Besides being slightly confusing, it makes it more annoying to grep for leftover occurrences of "sha1" in various files, because the header is included in so many places. Let's complete the transition by renaming the source and header files (and fixing up a few comment references). I kept the "-" in the name, as that seems to be our style; cf. fc1395f4a4 (sha1_file.c: rename to use dash in file name, 2018-04-10). We also have oidmap.h and oidset.h without any punctuation, but those are "struct oidmap" and "struct oidset" in the code. We _could_ make this "oidarray" to match, but somehow it looks uglier to me because of the length of "array" (plus it would be a very invasive patch for little gain). Signed-off-by: Jeff King <peff@peff.net> Signed-off-by: Junio C Hamano <gitster@pobox.com>
* Merge branch 'jk/oidhash'Junio C Hamano2019-07-101-12/+12
|\ | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | Code clean-up to remove hardcoded SHA-1 hash from many places. * jk/oidhash: hashmap: convert sha1hash() to oidhash() hash.h: move object_id definition from cache.h khash: rename oid helper functions khash: drop sha1-specific map types pack-bitmap: convert khash_sha1 maps into kh_oid_map delta-islands: convert island_marks khash to use oids khash: rename kh_oid_t to kh_oid_set khash: drop broken oid_map typedef object: convert create_object() to use object_id object: convert internal hash_obj() to object_id object: convert lookup_object() to use object_id object: convert lookup_unknown_object() to use object_id pack-objects: convert locate_object_entry_hash() to object_id pack-objects: convert packlist_find() to use object_id pack-bitmap-write: convert some helpers to use object_id upload-pack: rename a "sha1" variable to "oid" describe: fix accidental oid/hash type-punning
| * delta-islands: convert island_marks khash to use oidsJeff King2019-06-201-11/+11
| | | | | | | | | | | | | | | | | | All of the users of this map have an actual "struct object_id" rather than a bare sha1. Let's use the more descriptive type (and get one step closer to dropping khash_sha1 entirely). Signed-off-by: Jeff King <peff@peff.net> Signed-off-by: Junio C Hamano <gitster@pobox.com>
| * object: convert lookup_object() to use object_idJeff King2019-06-201-1/+1
| | | | | | | | | | | | | | | | | | | | | | | | | | There are no callers left of lookup_object() that aren't just passing us the "hash" member of a "struct object_id". Let's take the whole struct, which gets us closer to removing all raw sha1 variables. It also matches the existing conversions of lookup_blob(), etc. The conversions of callers were done by hand, but they're all mechanical one-liners. Signed-off-by: Jeff King <peff@peff.net> Signed-off-by: Junio C Hamano <gitster@pobox.com>
* | delta-islands: respect progress flagJeff King2019-06-201-2/+3
|/ | | | | | | | | | | | The delta island code always prints "Marked %d islands", even if progress has been suppressed with --no-progress or by sending stderr to a non-tty. Let's pass a progress boolean to load_delta_islands(). We already do the same thing for the progress meter in resolve_tree_islands(). Signed-off-by: Jeff King <peff@peff.net> Signed-off-by: Junio C Hamano <gitster@pobox.com>
* tree-walk: store object_id in a separate memberbrian m. carlson2019-01-151-1/+1
| | | | | | | | | | | | | | | | | When parsing a tree, we read the object ID directly out of the tree buffer. This is normally fine, but such an object ID cannot be used with oidcpy, which copies GIT_MAX_RAWSZ bytes, because if we are using SHA-1, there may not be that many bytes to copy. Instead, store the object ID in a separate struct member. Since we can no longer efficiently compute the path length, store that information as well in struct name_entry. Ensure we only copy the object ID into the new buffer if the path length is nonzero, as some callers will pass us an empty path with no object ID following it, and we will not want to read past the end of the buffer. Signed-off-by: brian m. carlson <sandals@crustytoothpaste.net> Signed-off-by: Junio C Hamano <gitster@pobox.com>
* delta-islands.c: remove the_repository referencesNguyễn Thái Ngọc Duy2018-11-121-10/+14
| | | | | Signed-off-by: Nguyễn Thái Ngọc Duy <pclouds@gmail.com> Signed-off-by: Junio C Hamano <gitster@pobox.com>
* pack-objects: move 'layer' into 'struct packing_data'Christian Couder2018-08-161-2/+2
| | | | | | | | | | | | | | This reduces the size of 'struct object_entry' from 88 bytes to 80 and therefore makes packing objects more efficient. For example on a Linux repo with 12M objects, `git pack-objects --all` needs extra 96MB memory even if the layer feature is not used. Helped-by: Jeff King <peff@peff.net> Helped-by: Duy Nguyen <pclouds@gmail.com> Signed-off-by: Christian Couder <chriscool@tuxfamily.org> Signed-off-by: Junio C Hamano <gitster@pobox.com>
* pack-objects: move tree_depth into 'struct packing_data'Christian Couder2018-08-161-9/+18
| | | | | | | | | | | | | | This reduces the size of 'struct object_entry' and therefore makes packing objects more efficient. This also renames cmp_tree_depth() into tree_depth_compare(), as it is more modern to have the name of the compare functions end with "compare". Helped-by: Jeff King <peff@peff.net> Helped-by: Duy Nguyen <pclouds@gmail.com> Signed-off-by: Christian Couder <chriscool@tuxfamily.org> Signed-off-by: Junio C Hamano <gitster@pobox.com>
* Add delta-islands.{c,h}Jeff King2018-08-161-0/+493
Hosting providers that allow users to "fork" existing repos want those forks to share as much disk space as possible. Alternates are an existing solution to keep all the objects from all the forks into a unique central repo, but this can have some drawbacks. Especially when packing the central repo, deltas will be created between objects from different forks. This can make cloning or fetching a fork much slower and much more CPU intensive as Git might have to compute new deltas for many objects to avoid sending objects from a different fork. Because the inefficiency primarily arises when an object is deltified against another object that does not exist in the same fork, we partition objects into sets that appear in the same fork, and define "delta islands". When finding delta base, we do not allow an object outside the same island to be considered as its base. So "delta islands" is a way to store objects from different forks in the same repo and packfile without having deltas between objects from different forks. This patch implements the delta islands mechanism in "delta-islands.{c,h}", but does not yet make use of it. A few new fields are added in 'struct object_entry' in "pack-objects.h" though. The documentation will follow in a patch that actually uses delta islands in "builtin/pack-objects.c". Signed-off-by: Jeff King <peff@peff.net> Signed-off-by: Christian Couder <chriscool@tuxfamily.org> Signed-off-by: Junio C Hamano <gitster@pobox.com>