Re: [RFC PATCH 5/6] Integrate hash algorithm support with repo setup

[Stefan Beller <sbeller@google.com>]

On Sun, Aug 20, 2017 at 5:00 PM, brian m. carlson
<sandals@crustytoothpaste.net> wrote:
> In future versions of Git, we plan to support an additional hash
> algorithm.  Integrate the enumeration of hash algorithms with repository
> setup, and store a pointer to the enumerated data in struct repository.
> Of course, we currently only support SHA-1, so hard-code this value in
> read_repository_format.  In the future, we'll enumerate this value from
> the configuration.
>
> Add a constant, current_hash, which points to the hash_algo structure
> pointer in the repository global.  Include repository.h in cache.h since
> we now need to have access to these struct and variable definitions.
>
> Signed-off-by: brian m. carlson <sandals@crustytoothpaste.net>

The new code seems to fit in nicely with the repository struct.

In another series I also included repository.h in cache.h
(not yet sent out), so I think that is a good idea.

> ---
>  cache.h      | 4 ++++
>  repository.c | 7 +++++++
>  repository.h | 5 +++++
>  setup.c      | 2 ++
>  4 files changed, 18 insertions(+)
>
> diff --git a/cache.h b/cache.h
> index 375a7fb15e..d759824803 100644
> --- a/cache.h
> +++ b/cache.h
> @@ -13,6 +13,7 @@
>  #include "hash.h"
>  #include "path.h"
>  #include "sha1-array.h"
> +#include "repository.h"
>
>  #ifndef platform_SHA_CTX
>  /*
> @@ -112,6 +113,8 @@ struct git_hash_algo {
>  };
>  extern const struct git_hash_algo hash_algos[1];
>
> +#define current_hash the_repository->hash_algo
> +
>  #if defined(DT_UNKNOWN) && !defined(NO_D_TYPE_IN_DIRENT)
>  #define DTYPE(de)      ((de)->d_type)
>  #else
> @@ -894,6 +897,7 @@ struct repository_format {
>         int version;
>         int precious_objects;
>         int is_bare;
> +       int hash_algo;
>         char *work_tree;
>         struct string_list unknown_extensions;
>  };
> diff --git a/repository.c b/repository.c
> index 1617467568..37764f627a 100644
> --- a/repository.c
> +++ b/repository.c
> @@ -62,6 +62,11 @@ void repo_set_gitdir(struct repository *repo, const char *path)
>         repo_setup_env(repo);
>  }
>
> +void repo_set_hash_algo(struct repository *repo, int hash_algo)
> +{
> +       repo->hash_algo = &hash_algos[hash_algo];
> +}
> +
>  /*
>   * Attempt to resolve and set the provided 'gitdir' for repository 'repo'.
>   * Return 0 upon success and a non-zero value upon failure.
> @@ -134,6 +139,8 @@ int repo_init(struct repository *repo, const char *gitdir, const char *worktree)
>         if (read_and_verify_repository_format(&format, repo->commondir))
>                 goto error;
>
> +       repo->hash_algo = &hash_algos[format.hash_algo];
> +
>         if (worktree)
>                 repo_set_worktree(repo, worktree);
>
> diff --git a/repository.h b/repository.h
> index 417787f3ef..f171172150 100644
> --- a/repository.h
> +++ b/repository.h
> @@ -4,6 +4,7 @@
>  struct config_set;
>  struct index_state;
>  struct submodule_cache;
> +struct git_hash_algo;
>
>  struct repository {
>         /* Environment */
> @@ -67,6 +68,9 @@ struct repository {
>          */
>         struct index_state *index;
>
> +       /* Repository's current hash algorithm. */
> +       const struct git_hash_algo *hash_algo;
> +
>         /* Configurations */
>         /*
>          * Bit used during initialization to indicate if repository state (like
> @@ -86,6 +90,7 @@ extern struct repository *the_repository;
>
>  extern void repo_set_gitdir(struct repository *repo, const char *path);
>  extern void repo_set_worktree(struct repository *repo, const char *path);
> +extern void repo_set_hash_algo(struct repository *repo, int algo);
>  extern int repo_init(struct repository *repo, const char *gitdir, const char *worktree);
>  extern int repo_submodule_init(struct repository *submodule,
>                                struct repository *superproject,
> diff --git a/setup.c b/setup.c
> index 115e70a4e8..289e24811c 100644
> --- a/setup.c
> +++ b/setup.c
> @@ -491,6 +491,7 @@ int read_repository_format(struct repository_format *format, const char *path)
>         memset(format, 0, sizeof(*format));
>         format->version = -1;
>         format->is_bare = -1;
> +       format->hash_algo = GIT_HASH_SHA1;
>         string_list_init(&format->unknown_extensions, 1);
>         git_config_from_file(check_repo_format, path, format);
>         return format->version;
> @@ -1125,6 +1126,7 @@ const char *setup_git_directory_gently(int *nongit_ok)
>                         repo_set_gitdir(the_repository, gitdir);
>                         setup_git_env();
>                 }
> +               repo_set_hash_algo(the_repository, repo_fmt.hash_algo);
>         }
>
>         strbuf_release(&dir);