[PATCH v2 2/7] repo-settings: add submodule_propagate_branches

From: Glen Choo via GitGitGadget <gitgitgadget@gmail.com>
Date: Oct 20, 2022, 20:20 UTC
Message-ID: <20499c62065d640b57bdcfd959e10b214f7e7297.1666297239.git.gitgitgadget@gmail.com>
In-Reply-To: <pull.1321.v2.git.git.1666297238.gitgitgadget@gmail.com>

From: Glen Choo <chooglen@google.com>

When processes recurse into submodules, the child processes have to use the same value of "submodule.propagateBranches" as the parent process regardless of whether the process is spawned in the superproject or submodule, otherwise the behavior may be inconsistent if the repositories don't agree on the config.

We haven't needed a way to propagate the config because the only command that reads "submodule.propagateBranches" is "git branch", which only has one mode of operation with "--recurse-submodules". However, a future commit will teach "submodule.propagateBranches" to "git submodule update", making this necessary.

Propagate "submodule.propagateBranches" to child processes by adding a corresponding GIT_INTERNAL_* environment variable and repository setting, and setting the environment variable inside prepare_submodule_repo_env(). Then, refactor builtin/branch.c to read the repository setting.

Using an internal environment variable is a potentially leaky abstraction because environment variables can come from sources besides the parent process. A more robust solution would be to teach Git that the repository is a submodule and to only read "submodule.propagateBranches" from the superproject config. There is WIP for this on the ML [1].

Another alternative would be to pass "-c submodule.propagateBranches" to all child processes. This is error-prone because many different processes are invoked directly or indirectly by "git submodule update" (e.g. "git submodule--helper clone", "git clone", "git checkout"). With an environment variable, we can avoid this work because prepare_submodule_repo_env() is already called for submodule child processes.

[1] https://lore.kernel.org/git/20220310004423.2627181-1-emilyshaffer@google.com/

Signed-off-by: Glen Choo <chooglen@google.com>
---
 builtin/branch.c | 11 +++--------
 cache.h          |  1 +
 repo-settings.c  | 10 ++++++++++
 repository.h     |  1 +
 submodule.c      |  2 ++
 5 files changed, 17 insertions(+), 8 deletions(-)

diff --git a/builtin/branch.c b/builtin/branch.c
index e0e0af43202..8279d4eeb15 100644
--- a/builtin/branch.c
+++ b/builtin/branch.c
@@ -40,7 +40,6 @@ static const char * const builtin_branch_usage[] = {
 static const char *head;
 static struct object_id head_oid;
 static int recurse_submodules = 0;
-static int submodule_propagate_branches = 0;
 
 static int branch_use_color = -1;
 static char branch_colors[][COLOR_MAXLEN] = {
@@ -106,10 +105,6 @@ static int git_branch_config(const char *var, const char *value, void *cb)
 		recurse_submodules = git_config_bool(var, value);
 		return 0;
 	}
-	if (!strcasecmp(var, "submodule.propagateBranches")) {
-		submodule_propagate_branches = git_config_bool(var, value);
-		return 0;
-	}
 
 	return git_color_default_config(var, value, cb);
 }
@@ -723,7 +718,7 @@ int cmd_branch(int argc, const char **argv, const char *prefix)
 
 	argc = parse_options(argc, argv, prefix, options, builtin_branch_usage,
 			     0);
-
+	prepare_repo_settings(the_repository);
 	if (!delete && !rename && !copy && !edit_description && !new_upstream &&
 	    !show_current && !unset_upstream && argc == 0)
 		list = 1;
@@ -739,7 +734,7 @@ int cmd_branch(int argc, const char **argv, const char *prefix)
 		usage_with_options(builtin_branch_usage, options);
 
 	if (recurse_submodules_explicit) {
-		if (!submodule_propagate_branches)
+		if (!the_repository->settings.submodule_propagate_branches)
 			die(_("branch with --recurse-submodules can only be used if submodule.propagateBranches is enabled"));
 		if (noncreate_actions)
 			die(_("--recurse-submodules can only be used to create branches"));
@@ -747,7 +742,7 @@ int cmd_branch(int argc, const char **argv, const char *prefix)
 
 	recurse_submodules =
 		(recurse_submodules || recurse_submodules_explicit) &&
-		submodule_propagate_branches;
+		the_repository->settings.submodule_propagate_branches;
 
 	if (filter.abbrev == -1)
 		filter.abbrev = DEFAULT_ABBREV;
diff --git a/cache.h b/cache.h
index 26ed03bd6de..151e1d49e77 100644
--- a/cache.h
+++ b/cache.h
@@ -505,6 +505,7 @@ static inline enum object_type object_type(unsigned int mode)
 #define GIT_WORK_TREE_ENVIRONMENT "GIT_WORK_TREE"
 #define GIT_PREFIX_ENVIRONMENT "GIT_PREFIX"
 #define GIT_SUPER_PREFIX_ENVIRONMENT "GIT_INTERNAL_SUPER_PREFIX"
+#define GIT_SUBMODULE_PROPAGATE_BRANCHES_ENVIRONMENT "GIT_INTERNAL_SUBMODULE_PROPAGATE_BRANCHES"
 #define DEFAULT_GIT_DIR_ENVIRONMENT ".git"
 #define DB_ENVIRONMENT "GIT_OBJECT_DIRECTORY"
 #define INDEX_ENVIRONMENT "GIT_INDEX_FILE"
diff --git a/repo-settings.c b/repo-settings.c
index e8b58151bc4..180df14e45f 100644
--- a/repo-settings.c
+++ b/repo-settings.c
@@ -71,6 +71,16 @@ void prepare_repo_settings(struct repository *r)
 	if (git_env_bool(GIT_TEST_MULTI_PACK_INDEX, 0))
 		r->settings.core_multi_pack_index = 1;
 
+	/*
+	 * If the environment variable is set, assume that it came from the
+	 * superproject and ignore the config.
+	 */
+	r->settings.submodule_propagate_branches =
+		git_env_bool(GIT_SUBMODULE_PROPAGATE_BRANCHES_ENVIRONMENT, -1);
+	if (r->settings.submodule_propagate_branches == -1)
+		repo_cfg_bool(r, "submodule.propagateBranches",
+			      &r->settings.submodule_propagate_branches, 0);
+
 	/*
 	 * Non-boolean config
 	 */
diff --git a/repository.h b/repository.h
index 24316ac944e..3df6fdbdd5c 100644
--- a/repository.h
+++ b/repository.h
@@ -37,6 +37,7 @@ struct repo_settings {
 	int fetch_write_commit_graph;
 	int command_requires_full_index;
 	int sparse_index;
+	int submodule_propagate_branches;
 
 	struct fsmonitor_settings *fsmonitor; /* lazily loaded */
 
diff --git a/submodule.c b/submodule.c
index bf7a2c79183..624404957fa 100644
--- a/submodule.c
+++ b/submodule.c
@@ -503,6 +503,8 @@ static void print_submodule_diff_summary(struct repository *r, struct rev_info *
 
 void prepare_submodule_repo_env(struct strvec *out)
 {
+	if (the_repository->settings.submodule_propagate_branches)
+		strvec_pushf(out, "%s=1", GIT_SUBMODULE_PROPAGATE_BRANCHES_ENVIRONMENT);
 	prepare_other_repo_env(out, DEFAULT_GIT_DIR_ENVIRONMENT);
 }

-- 
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