scalar: annotate config file with "set by scalar"

A repo may have config options set by 'scalar clone' or 'scalar
register' and then updated by 'scalar reconfigure'. It can be helpful to
point out which of those options were set by the latest scalar
recommendations.

Add "# set by scalar" to the end of each config option to assist users
in identifying why these config options were set in their repo. Use a new
helper method to simplify the two callsites.

Co-authored-by: Patrick Steinhardt <ps@pks.im>
Signed-off-by: Patrick Steinhardt <ps@pks.im>
Signed-off-by: Derrick Stolee <stolee@gmail.com>

Author: derrickstolee

scalar.c

@@ -19,6 +19,7 @@
 #include "help.h"
 #include "setup.h"
 #include "trace2.h"
+#include "path.h"
 
 static void setup_enlistment_directory(int argc, const char **argv,
 				       const char * const *usagestr,
@@ -95,6 +96,16 @@ struct scalar_config {
 	int overwrite_on_reconfigure;
 };
 
+static int set_config_with_comment(const char *key, const char *value)
+{
+	char *file = repo_git_path(the_repository, "config");
+	int res = repo_config_set_multivar_in_file_gently(the_repository, file,
+							  key, value, NULL,
+							  " # set by scalar", 0);
+	free(file);
+	return res;
+}
+
 static int set_scalar_config(const struct scalar_config *config, int reconfigure)
 {
 	char *value = NULL;
@@ -103,7 +114,7 @@ static int set_scalar_config(const struct scalar_config *config, int reconfigure
 	if ((reconfigure && config->overwrite_on_reconfigure) ||
 	    repo_config_get_string(the_repository, config->key, &value)) {
 		trace2_data_string("scalar", the_repository, config->key, "created");
-		res = repo_config_set_gently(the_repository, config->key, config->value);
+		res = set_config_with_comment(config->key, config->value);
 	} else {
 		trace2_data_string("scalar", the_repository, config->key, "exists");
 		res = 0;
@@ -197,9 +208,8 @@ static int set_recommended_config(int reconfigure)
 	if (repo_config_get_string(the_repository, "log.excludeDecoration", &value)) {
 		trace2_data_string("scalar", the_repository,
 				   "log.excludeDecoration", "created");
-		if (repo_config_set_multivar_gently(the_repository, "log.excludeDecoration",
-						    "refs/prefetch/*",
-						    CONFIG_REGEX_NONE, 0))
+		if (set_config_with_comment("log.excludeDecoration",
+					    "refs/prefetch/*"))
 			return error(_("could not configure "
 				       "log.excludeDecoration"));
 	} else {

t/t9210-scalar.sh

@@ -210,6 +210,9 @@ test_expect_success 'scalar reconfigure' '
 	GIT_TRACE2_EVENT="$(pwd)/reconfigure" scalar reconfigure -a &&
 	test_path_is_file one/src/cron.txt &&
 	test true = "$(git -C one/src config core.preloadIndex)" &&
+	test_grep "preloadIndex = true # set by scalar" one/src/.git/config &&
+	test_grep "excludeDecoration = refs/prefetch/\* # set by scalar" one/src/.git/config &&
+
 	test_subcommand git maintenance start <reconfigure &&
 	test_subcommand ! git maintenance unregister --force <reconfigure &&