Read arguments with fish -c

This reads any additional positional arguments given to `fish -c` into
$argv.

We don't handle the first argument specially (as `$0`) as that's confusing and
doesn't seem very useful.

Fixes #2314.

doc_src/cmds/fish.rst

@@ -8,7 +8,7 @@ Synopsis
 
 ::
 
-    fish [OPTIONS] [-c command] [FILE [ARGUMENTS...]]
+    fish [OPTIONS] [-c command] [FILE] [ARGUMENTS...]
 
 Description
 -----------
@@ -17,7 +17,7 @@ fish is a command-line shell written mainly with interactive use in mind. This p
 
 The following options are available:
 
-- ``-c`` or ``--command=COMMANDS`` evaluate the specified commands instead of reading from the commandline
+- ``-c`` or ``--command=COMMANDS`` evaluate the specified commands instead of reading from the commandline, passing any additional positional arguments via :ref:`$argv <variables-argv>`. Note that, unlike other shells, the first argument is *not* the name of the program (``$0``), but simply the first normal argument.
 
 - ``-C`` or ``--init-command=COMMANDS`` evaluate the specified commands after reading the configuration, before running the command specified by ``-c`` or reading interactive input
 

src/fish.cpp

@@ -489,6 +489,14 @@ int main(int argc, char **argv) {
             fish_xdm_login_hack_hack_hack_hack(&opts.batch_cmds, argc - my_optind,
                                                argv + my_optind);
         }
+
+        // Pass additional args as $argv.
+        // Note that we *don't* support setting argv[0]/$0, unlike e.g. bash.
+        wcstring_list_t list;
+        for (char **ptr = argv + my_optind; *ptr; ptr++) {
+            list.push_back(str2wcstring(*ptr));
+        }
+        parser.vars().set(L"argv", ENV_DEFAULT, std::move(list));
         res = run_command_list(parser, &opts.batch_cmds, {});
         parser.libdata().exit_current_script = false;
     } else if (my_optind == argc) {

tests/checks/invocation.fish

@@ -38,3 +38,8 @@ $fish -c 'if status --is-login ; echo login shell ; else ; echo not login shell
 $fish -c 'if status --is-login ; echo login shell ; else ; echo not login shell ; end; if status --is-interactive ; echo interactive ; else ; echo not interactive ; end' -l
 # CHECK: login shell
 # CHECK: not interactive
+
+$fish -c 'string escape $argv' 1 2 3
+# CHECK: 1
+# CHECK: 2
+# CHECK: 3