Simplify error path in config_set

Many error paths freed their local data althought it is freed later on
when the end of the function notices that there was an error. This can
cause double frees and invalid memory access.

Signed-off-by: Carlos Martín Nieto <cmn@elego.de>

src/config.c

@@ -285,27 +285,23 @@ static int config_set(git_config *cfg, const char *name, const char *value)
 	 */
 
 	var = git__malloc(sizeof(git_cvar));
-	if(var == NULL){
-		error = GIT_ENOMEM;
-		goto out;
-	}
+	if (var == NULL)
+		return GIT_ENOMEM;
+
+	memset(var, 0x0, sizeof(git_cvar));
 
 	var->name = git__strdup(name);
-	if(var->name == NULL){
+	if (var->name == NULL) {
 		error = GIT_ENOMEM;
-		free(var);
 		goto out;
 	}
 
 	var->value = value ? git__strdup(value) : NULL;
 	if (var->value == NULL && value != NULL) {
 		error = GIT_ENOMEM;
-		cvar_free(var);
 		goto out;
 	}
 
-	var->next = NULL;
-
 	CVAR_LIST_APPEND(&cfg->var_list, var);
 
  out:
@@ -313,7 +309,6 @@ static int config_set(git_config *cfg, const char *name, const char *value)
 		cvar_free(var);
 
 	return error;
-
 }
 
 int git_config_set_int(git_config *cfg, const char *name, int value)