Pass `--global` when calling `git config --get`, for consistency with `git config --set` (#23157) (#23199)

Backport #23157

This arose out of #22451; it seems we are checking using non-global
settings to see if a config value is set, in order to decide whether to
call another global(-indeed) configuration command. This PR changes it
so that both the check and the set are for global configuration.

Co-authored-by: Philip Peterson <philip-peterson@users.noreply.github.com>

modules/git/git.go

@@ -312,7 +312,7 @@ func CheckGitVersionAtLeast(atLeast string) error {
 }
 
 func configSet(key, value string) error {
-	stdout, _, err := NewCommand(DefaultContext, "config", "--get").AddDynamicArguments(key).RunStdString(nil)
+	stdout, _, err := NewCommand(DefaultContext, "config", "--global", "--get").AddDynamicArguments(key).RunStdString(nil)
 	if err != nil && !err.IsExitCode(1) {
 		return fmt.Errorf("failed to get git config %s, err: %w", key, err)
 	}
@@ -331,7 +331,7 @@ func configSet(key, value string) error {
 }
 
 func configSetNonExist(key, value string) error {
-	_, _, err := NewCommand(DefaultContext, "config", "--get").AddDynamicArguments(key).RunStdString(nil)
+	_, _, err := NewCommand(DefaultContext, "config", "--global", "--get").AddDynamicArguments(key).RunStdString(nil)
 	if err == nil {
 		// already exist
 		return nil
@@ -349,7 +349,7 @@ func configSetNonExist(key, value string) error {
 }
 
 func configAddNonExist(key, value string) error {
-	_, _, err := NewCommand(DefaultContext, "config", "--get").AddDynamicArguments(key, regexp.QuoteMeta(value)).RunStdString(nil)
+	_, _, err := NewCommand(DefaultContext, "config", "--global", "--get").AddDynamicArguments(key, regexp.QuoteMeta(value)).RunStdString(nil)
 	if err == nil {
 		// already exist
 		return nil
@@ -366,7 +366,7 @@ func configAddNonExist(key, value string) error {
 }
 
 func configUnsetAll(key, value string) error {
-	_, _, err := NewCommand(DefaultContext, "config", "--get").AddDynamicArguments(key).RunStdString(nil)
+	_, _, err := NewCommand(DefaultContext, "config", "--global", "--get").AddDynamicArguments(key).RunStdString(nil)
 	if err == nil {
 		// exist, need to remove
 		_, _, err = NewCommand(DefaultContext, "config", "--global", "--unset-all").AddDynamicArguments(key, regexp.QuoteMeta(value)).RunStdString(nil)