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

["brian m. carlson" <sandals@xxxxxxxxxxxxxxxxxxxx>]

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@xxxxxxxxxxxxxxxxxxxx>
---
 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);