Teach string repeat to handle multiple arguments

Each argument in string repeat is handled independently, except that the
--no-newline option applies only to the last newline.

Fixes #5988

CHANGELOG.rst

@@ -103,6 +103,7 @@ Scripting improvements
 - ``math`` learned bitwise functions ``bitand``, ``bitor`` and ``bitxor``, used like ``math "bitand(0xFE, 5)"`` (:issue:`7281`).
 - ``math`` learned tau for those wishing to cut down on typing "2 * pi".
 - ``string`` subcommands now quit early when used with ``--quiet`` (:issue:`7495`).
+- ``string repeat`` now handles multiple arguments, repeating each one (:issue:`5988`).
 -  Failed redirections will now set ``$status`` (:issue:`7540`).
 -  More consistent $status after errors, including invalid expansions like ``$foo[``.
 -  ``read`` can now read interactively from other files, so e.g. forcing it to read from the terminal via ``read </dev/tty`` works (:issue:`7358`).

src/builtin_string.cpp

@@ -1559,9 +1559,14 @@ static int string_repeat(parser_t &parser, io_streams_t &streams, int argc, wcha
     if (retval != STATUS_CMD_OK) return retval;
 
     bool all_empty = true;
+    bool first = true;
 
     arg_iterator_t aiter(argv, optind, streams);
-    if (const wcstring *word = aiter.nextstr()) {
+    while (const wcstring *word = aiter.nextstr()) {
+        if (!first && !opts.quiet) {
+            streams.out.append(L'\n');
+        }
+        first = false;
         const bool limit_repeat =
             (opts.max > 0 && word->length() * opts.count > static_cast<size_t>(opts.max)) ||
             !opts.count;
@@ -1574,6 +1579,8 @@ static int string_repeat(parser_t &parser, io_streams_t &streams, int argc, wcha
                 return STATUS_CMD_OK;
             }
         }
+
+        // Append if not quiet.
         if (!opts.quiet) {
             streams.out.append(repeated);
         }

tests/checks/string.fish

@@ -411,6 +411,27 @@ string repeat -n3 -m20 foo
 string repeat -m4 foo
 # CHECK: foof
 
+string repeat -n 5 a b c
+# CHECK: aaaaa
+# CHECK: bbbbb
+# CHECK: ccccc
+
+string repeat -n 5 --max 4 123 456 789
+# CHECK: 1231
+# CHECK: 4564
+# CHECK: 7897
+
+string repeat -n 5 --max 4 123 '' 789
+# CHECK: 1231
+# CHECK:
+# CHECK: 7897
+
+# Historical string repeat behavior is no newline if no output.
+echo -n before
+string repeat -n 5 ''
+echo after
+# CHECK: beforeafter
+
 string repeat -n-1 foo; and echo "exit 0"
 # CHECKERR: string repeat: Invalid count value '-1'