From 667d251a04c1dd769fb5a71bbe94d6d15ae594f1 Mon Sep 17 00:00:00 2001 From: "brian m. carlson" Date: Tue, 1 Jul 2025 21:22:30 +0000 Subject: Use legacy hash for legacy formats We have a large variety of data formats and protocols where no hash algorithm was defined and the default was assumed to always be SHA-1. Instead of explicitly stating SHA-1, let's use the constant to represent the legacy hash algorithm (which is still SHA-1) so that it's clear for documentary purposes that it's a legacy fallback option and not an intentional choice to use SHA-1. Signed-off-by: brian m. carlson Signed-off-by: Junio C Hamano --- setup.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-) (limited to 'setup.c') diff --git a/setup.c b/setup.c index f93bd6a24a..3d2b3e745b 100644 --- a/setup.c +++ b/setup.c @@ -2222,11 +2222,11 @@ void initialize_repository_version(int hash_algo, * version will get adjusted by git-clone(1) once it has learned about * the remote repository's format. */ - if (hash_algo != GIT_HASH_SHA1 || + if (hash_algo != GIT_HASH_SHA1_LEGACY || ref_storage_format != REF_STORAGE_FORMAT_FILES) target_version = GIT_REPO_VERSION_READ; - if (hash_algo != GIT_HASH_SHA1 && hash_algo != GIT_HASH_UNKNOWN) + if (hash_algo != GIT_HASH_SHA1_LEGACY && hash_algo != GIT_HASH_UNKNOWN) git_config_set("extensions.objectformat", hash_algos[hash_algo].name); else if (reinit) -- cgit v1.2.3 From d6e616cee741fc3f67fd3b7c328175b932d0aaa5 Mon Sep 17 00:00:00 2001 From: "brian m. carlson" Date: Tue, 1 Jul 2025 21:22:31 +0000 Subject: setup: use the default algorithm to initialize repo format When we define a new repository format with REPOSITORY_FORMAT_INIT, we always use GIT_HASH_SHA1, and this value ends up getting used as the default value to initialize a repository if none of the command line, environment, or config tell us to do otherwise. Because we might not always want to use SHA-1 as the default, let's instead specify the default hash algorithm constant so that we will use whatever the specified default is. However, we also need to continue to read older repositories. If we're in a v0 repository or extensions.objectformat is not set, then we must continue to default to the original hash algorithm: SHA-1. If an algorithm is set explicitly, however, it will override the hash_algo member of the repository_format struct and we'll get the right value. Similarly, if the repository was initialized before Git 0.99.3, then it may lack a core.repositoryformatversion key, and some repositories lack a config file altogether. In both cases, format->version is -1 and we need to assume that SHA-1 is in use. Because clear_repository_format reinitializes the struct repository_format and therefore sets the hash_algo member to the default (which could in the future not be SHA-1), we need to reset this member explicitly. We know, however, that at the point we call read_repository_format, we are actually reading an existing repository and not initializing a new one or operating outside of a repository, so we are not changing the default behavior back to SHA-1 if the default algorithm is different. It is potentially questionable that we ignore all repository configuration if there is a config file but it doesn't have core.repositoryformatversion set, in which case we reset all of the configuration to the default. However, it is unclear what the right thing to do instead with such an old repository is and a simple git init will add the missing entry, so for now, we simply honor what the existing code does and reset the value to the default, simply adding our initialization to SHA-1. Signed-off-by: brian m. carlson Signed-off-by: Junio C Hamano --- setup.c | 5 ++++- setup.h | 2 +- 2 files changed, 5 insertions(+), 2 deletions(-) (limited to 'setup.c') diff --git a/setup.c b/setup.c index 3d2b3e745b..03a61bd06a 100644 --- a/setup.c +++ b/setup.c @@ -835,9 +835,12 @@ static void init_repository_format(struct repository_format *format) int read_repository_format(struct repository_format *format, const char *path) { clear_repository_format(format); + format->hash_algo = GIT_HASH_SHA1_LEGACY; git_config_from_file(check_repo_format, path, format); - if (format->version == -1) + if (format->version == -1) { clear_repository_format(format); + format->hash_algo = GIT_HASH_SHA1_LEGACY; + } return format->version; } diff --git a/setup.h b/setup.h index 18dc3b7368..8522fa8575 100644 --- a/setup.h +++ b/setup.h @@ -149,7 +149,7 @@ struct repository_format { { \ .version = -1, \ .is_bare = -1, \ - .hash_algo = GIT_HASH_SHA1, \ + .hash_algo = GIT_HASH_DEFAULT, \ .ref_storage_format = REF_STORAGE_FORMAT_FILES, \ .unknown_extensions = STRING_LIST_INIT_DUP, \ .v1_only_extensions = STRING_LIST_INIT_DUP, \ -- cgit v1.2.3