Partially revert c8aed5e8 (repository: stop setting SHA1 as the
default object hash, 2024-05-07), to keep end-user systems still
broken when we have gap in our test coverage but yet give them an
escape hatch to set the GIT_DEFAULT_HASH environment variable to
"sha1" in order to revert to the previous behaviour. This variable
has been in use for using SHA-256 hash by default, and it should be
a better fit than inventing a new and test-only knob.
Signed-off-by: Junio C Hamano <gitster@xxxxxxxxx>
---
environment.h | 1 +
repository.c | 40 ++++++++++++++++++++++++++++++++++++++++
setup.c | 2 --
3 files changed, 41 insertions(+), 2 deletions(-)
diff --git a/environment.h b/environment.h
index 05fd94d7be..deaa29408f 100644
--- a/environment.h
+++ b/environment.h
@@ -56,6 +56,7 @@ const char *getenv_safe(struct strvec *argv, const char *name);
#define GIT_OPTIONAL_LOCKS_ENVIRONMENT "GIT_OPTIONAL_LOCKS"
#define GIT_TEXT_DOMAIN_DIR_ENVIRONMENT "GIT_TEXTDOMAINDIR"
#define GIT_ATTR_SOURCE_ENVIRONMENT "GIT_ATTR_SOURCE"
+#define GIT_DEFAULT_HASH_ENVIRONMENT "GIT_DEFAULT_HASH"
/*
* Environment variable used in handshaking the wire protocol.
diff --git a/repository.c b/repository.c
index 15c10015b0..f912ee9a7c 100644
--- a/repository.c
+++ b/repository.c
@@ -1,5 +1,6 @@
#include "git-compat-util.h"
#include "abspath.h"
+#include "environment.h"
#include "repository.h"
#include "object-store-ll.h"
#include "config.h"
@@ -19,6 +20,27 @@
static struct repository the_repo;
struct repository *the_repository = &the_repo;
+static void set_default_hash_algo(struct repository *repo)
+{
+ const char *hash_name;
+ int algo;
+
+ hash_name = getenv(GIT_DEFAULT_HASH_ENVIRONMENT);
+ if (!hash_name)
+ return;
+ algo = hash_algo_by_name(hash_name);
+
+ /*
+ * NEEDSWORK: after all, falling back to SHA-1 by assigning
+ * GIT_HASH_SHA1 to algo here, instead of returning, may give
+ * us better behaviour.
+ */
+ if (algo == GIT_HASH_UNKNOWN)
+ return;
+
+ repo_set_hash_algo(repo, algo);
+}
+
void initialize_repository(struct repository *repo)
{
repo->objects = raw_object_store_new();
@@ -26,6 +48,24 @@ void initialize_repository(struct repository *repo)
repo->parsed_objects = parsed_object_pool_new();
ALLOC_ARRAY(repo->index, 1);
index_state_init(repo->index, repo);
+
+ /*
+ * When a command runs inside a repository, it learns what
+ * hash algorithm is in use from the repository, but some
+ * commands are designed to work outside a repository, yet
+ * they want to access the_hash_algo, if only for the length
+ * of the hashed value to see if their input looks like a
+ * plausible hash value.
+ *
+ * We are in the process of identifying the codepaths and
+ * giving them an appropriate default individually; any
+ * unconverted codepath that tries to access the_hash_algo
+ * will thus fail. The end-users however have an escape hatch
+ * to set GIT_DEFAULT_HASH environment variable to "sha1" get
+ * back the old behaviour of defaulting to SHA-1.
+ */
+ if (repo == the_repository)
+ set_default_hash_algo(repo);
}
static void expand_base_dir(char **out, const char *in,
diff --git a/setup.c b/setup.c
index 7c996659bd..d084703465 100644
--- a/setup.c
+++ b/setup.c
@@ -1840,8 +1840,6 @@ int daemonize(void)
#define TEST_FILEMODE 1
#endif
-#define GIT_DEFAULT_HASH_ENVIRONMENT "GIT_DEFAULT_HASH"
-
static void copy_templates_1(struct strbuf *path, struct strbuf *template_path,
DIR *dir)
{
--
2.45.0-145-g3e4a232f6e
