config: skip worktree config in get_backend_for_use

vermiculus · vermiculus · commit f4b11136eb34 · 2024-02-21T09:27:32.000-06:00
It would seem that `get_backend_for_use` is primarily used when
writing config data -- either to set keys or delete them (based on the
possible values of `backend_use`). When git-config(1) is used for
side-effects, it will modify only the local (repository-level)
configuration unless explicitly overridden.

From git-config(1):

    --local
        For writing options: write to the repository .git/config file.
	This is the default behavior.

`get_backend_for_use` does not have the ability to specify a config
level and typically is expected (it seems) to 'do the right thing'.
Taking its cue from git-config(1), don't update worktree-specific
config unless it's the only option.

If that functionality is needed by consumers, I assume they would find
the appropriate backend with `git_config_open_level` and feed that
`git_config` object through to the `git_config_set_*` functions (as
demonstrated in the provided test).
diff --git a/src/libgit2/config.c b/src/libgit2/config.c
@@ -593,12 +593,14 @@ static int get_backend_for_use(git_config_backend **out,
 	git_config *cfg, const char *name, backend_use use)
 {
 	size_t i;
+	size_t len;
 	backend_internal *backend;
 	int error = 0;
 
 	*out = NULL;
 
-	if (git_vector_length(&cfg->backends) == 0) {
+	len = git_vector_length(&cfg->backends);
+	if (len == 0) {
 		git_error_set(GIT_ERROR_CONFIG,
 			"cannot %s value for '%s' when no config backends exist",
 			uses[use], name);
@@ -609,6 +611,15 @@ static int get_backend_for_use(git_config_backend **out,
 		if (backend->backend->readonly)
 			continue;
 
+		/* git-config doesn't update worktree-level config
+		   unless specifically requested; follow suit. If you
+		   specifically want to update that level, open the
+		   single config level with git_config_open_level and
+		   provide that as the config. In this case, there
+		   will only be one backend in the config. */
+		if (len > 1 && backend->level == GIT_CONFIG_LEVEL_WORKTREE)
+			continue;
+
 		*out = backend->backend;
 		goto cleanup;
 	}
diff --git a/tests/libgit2/worktree/config.c b/tests/libgit2/worktree/config.c
@@ -27,7 +27,7 @@ void test_worktree_config__open(void)
 	git_config_free(cfg);
 }
 
-void test_worktree_config__set(void)
+void test_worktree_config__set_level_local(void)
 {
 	git_config *cfg;
 	int32_t val;
@@ -45,3 +45,31 @@ void test_worktree_config__set(void)
 	cl_assert_equal_i(val, 5);
 	git_config_free(cfg);
 }
+
+void test_worktree_config__set_level_worktree(void)
+{
+	git_config *cfg;
+	git_config *wtcfg;
+	int32_t val;
+
+	cl_git_pass(git_repository_config(&cfg, fixture.repo));
+	cl_git_pass(git_config_open_level(&wtcfg, cfg, GIT_CONFIG_LEVEL_WORKTREE));
+	cl_git_pass(git_config_set_int32(wtcfg, "worktree.specific", 42));
+
+	cl_git_pass(git_config_get_int32(&val, cfg, "worktree.specific"));
+	cl_assert_equal_i(val, 42);
+
+	/* reopen to verify config has been set */
+	git_config_free(cfg);
+	cl_git_pass(git_repository_config(&cfg, fixture.repo));
+	cl_git_pass(git_config_get_int32(&val, cfg, "worktree.specific"));
+	cl_assert_equal_i(val, 42);
+
+	cl_assert(git_config_delete_entry(cfg, "worktree.specific") == GIT_ENOTFOUND);
+
+	cl_git_pass(git_config_delete_entry(wtcfg, "worktree.specific"));
+	cl_assert(git_config_get_int32(&val, cfg, "worktree.specific") == GIT_ENOTFOUND);
+
+	git_config_free(cfg);
+	git_config_free(wtcfg);
+}
