strv: introduce strv_copy_unless_empty()

src/basic/strv.c

@@ -123,6 +123,22 @@ char** strv_copy_n(char * const *l, size_t m) {
         return TAKE_PTR(result);
 }
 
+int strv_copy_unless_empty(char * const *l, char ***ret) {
+        assert(ret);
+
+        if (strv_isempty(l)) {
+                *ret = NULL;
+                return 0;
+        }
+
+        char **copy = strv_copy(l);
+        if (!copy)
+                return -ENOMEM;
+
+        *ret = TAKE_PTR(copy);
+        return 1;
+}
+
 size_t strv_length(char * const *l) {
         size_t n = 0;
 

src/basic/strv.h

@@ -38,6 +38,8 @@ char** strv_copy_n(char * const *l, size_t n);
 static inline char** strv_copy(char * const *l) {
         return strv_copy_n(l, SIZE_MAX);
 }
+int strv_copy_unless_empty(char * const *l, char ***ret);
+
 size_t strv_length(char * const *l) _pure_;
 
 int strv_extend_strv(char ***a, char * const *b, bool filter_duplicates);