Re: [PATCH] setup: warn if extensions exist on old format

[Junio C Hamano <gitster@pobox.com>]

Junio C Hamano <gitster@pobox.com> writes:

> An alternative may be to grandfather some extensions that were
> enabled by git by mistake without updating the format version, and
> we update the repository even if the repository has extensions that
> should not exist, but those offending extensions are limited only to
> those that we decide to special case.  That would make the end-user
> experience even smoother.
>
> Is extenions.worktreeCOnfig the only one that needs this escape
> hatch?

Assuming that worktreeconfig is the only thing, the change may look
like this.  With this change, we might want to drop the new warning
in hunk ll.542- to avoid encouraging people to muck with their
repository with random configuration variables that happen to share
extensions.* prefix with us.

 cache.h |  2 +-
 setup.c | 17 +++++++++++++----
 2 files changed, 14 insertions(+), 5 deletions(-)

diff --git a/cache.h b/cache.h
index e5885cc9ea..8ff46857f6 100644
--- a/cache.h
+++ b/cache.h
@@ -1042,8 +1042,8 @@ struct repository_format {
 	int worktree_config;
 	int is_bare;
 	int hash_algo;
-	int has_extensions;
 	char *work_tree;
+	int has_unallowed_extensions;
 	struct string_list unknown_extensions;
 };
 
diff --git a/setup.c b/setup.c
index eb066db6d8..5f4786d3b9 100644
--- a/setup.c
+++ b/setup.c
@@ -455,12 +455,13 @@ static int check_repo_format(const char *var, const char *value, void *vdata)
 	if (strcmp(var, "core.repositoryformatversion") == 0)
 		data->version = git_config_int(var, value);
 	else if (skip_prefix(var, "extensions.", &ext)) {
-		data->has_extensions = 1;
 		/*
 		 * record any known extensions here; otherwise,
 		 * we fall through to recording it as unknown, and
 		 * check_repository_format will complain
 		 */
+		int is_unallowed_extension = 1;
+
 		if (!strcmp(ext, "noop"))
 			;
 		else if (!strcmp(ext, "preciousobjects"))
@@ -469,10 +470,13 @@ static int check_repo_format(const char *var, const char *value, void *vdata)
 			if (!value)
 				return config_error_nonbool(var);
 			data->partial_clone = xstrdup(value);
-		} else if (!strcmp(ext, "worktreeconfig"))
+		} else if (!strcmp(ext, "worktreeconfig")) {
 			data->worktree_config = git_config_bool(var, value);
-		else
+			is_unallowed_extension = 0;
+		} else
 			string_list_append(&data->unknown_extensions, ext);
+
+		data->has_unallowed_extensions |= is_unallowed_extension;
 	}
 
 	return read_worktree_config(var, value, vdata);
@@ -542,6 +546,11 @@ static int check_repository_format_gently(const char *gitdir, struct repository_
 		}
 	}
 
+	if (candidate->version == 0 && candidate->has_unallowed_extensions) {
+		warning(_("some extensions are enabled, but core.repositoryFormatVersion=0"));
+		warning(_("if you intended to use extensions, run 'git config core.repositoryFormatVersion 1'"));
+	}
+
 	return 0;
 }
 
@@ -560,7 +569,7 @@ int upgrade_repository_format(int target_version)
 		return 0;
 
 	if (verify_repository_format(&repo_fmt, &err) < 0 ||
-	    (!repo_fmt.version && repo_fmt.has_extensions)) {
+	    (!repo_fmt.version && repo_fmt.has_unallowed_extensions)) {
 		warning("unable to upgrade repository format from %d to %d: %s",
 			repo_fmt.version, target_version, err.buf);
 		strbuf_release(&err);