[PATCH v2 4/5] setup: correctly reinitialize repository version

[Caleb White <cdwhite3@pm.me>]

When reinitializing a repository, Git does not account for extensions
other than `objectformat` and `refstorage` when determining the
repository version. This can lead to a repository being downgraded to
version 0 if extensions are set, causing Git future operations to fail.

This patch teaches Git to check if other extensions are defined in the
config to ensure that the repository version is set correctly.

Signed-off-by: Caleb White <cdwhite3@pm.me>
---
 setup.c | 32 +++++++++++++++++++++++---------
 1 file changed, 23 insertions(+), 9 deletions(-)

diff --git a/setup.c b/setup.c
index 7b648de0279116b381eea46800ad130606926103..1e5c2eacb19eb6b230d7c9954f66fc7ae0b05631 100644
--- a/setup.c
+++ b/setup.c
@@ -2204,8 +2204,8 @@ void initialize_repository_version(int hash_algo,
 				   enum ref_storage_format ref_storage_format,
 				   int reinit)
 {
-	char repo_version_string[10];
-	int repo_version = GIT_REPO_VERSION;
+	struct strbuf repo_version = STRBUF_INIT;
+	int target_version = GIT_REPO_VERSION;
 
 	/*
 	 * Note that we initialize the repository version to 1 when the ref
@@ -2216,12 +2216,7 @@ void initialize_repository_version(int hash_algo,
 	 */
 	if (hash_algo != GIT_HASH_SHA1 ||
 	    ref_storage_format != REF_STORAGE_FORMAT_FILES)
-		repo_version = GIT_REPO_VERSION_READ;
-
-	/* This forces creation of new config file */
-	xsnprintf(repo_version_string, sizeof(repo_version_string),
-		  "%d", repo_version);
-	git_config_set("core.repositoryformatversion", repo_version_string);
+		target_version = GIT_REPO_VERSION_READ;
 
 	if (hash_algo != GIT_HASH_SHA1 && hash_algo != GIT_HASH_UNKNOWN)
 		git_config_set("extensions.objectformat",
@@ -2234,6 +2229,25 @@ void initialize_repository_version(int hash_algo,
 			       ref_storage_format_to_name(ref_storage_format));
 	else if (reinit)
 		git_config_set_gently("extensions.refstorage", NULL);
+
+	if (reinit) {
+		struct strbuf config = STRBUF_INIT;
+		struct repository_format repo_fmt = REPOSITORY_FORMAT_INIT;
+
+		strbuf_git_common_path(&config, the_repository, "config");
+		read_repository_format(&repo_fmt, config.buf);
+
+		if (repo_fmt.v1_only_extensions.nr)
+			target_version = GIT_REPO_VERSION_READ;
+
+		strbuf_release(&config);
+		clear_repository_format(&repo_fmt);
+	}
+
+	strbuf_addf(&repo_version, "%d", target_version);
+	git_config_set("core.repositoryformatversion", repo_version.buf);
+
+	strbuf_release(&repo_version);
 }
 
 static int is_reinit(void)
@@ -2333,7 +2347,7 @@ static int create_default_files(const char *template_path,
 		adjust_shared_perm(repo_get_git_dir(the_repository));
 	}
 
-	initialize_repository_version(fmt->hash_algo, fmt->ref_storage_format, 0);
+	initialize_repository_version(fmt->hash_algo, fmt->ref_storage_format, reinit);
 
 	/* Check filemode trustability */
 	path = git_path_buf(&buf, "config");

-- 
2.47.0