fix: point a declined download at the c entry

Saying no to a large download sent a beginner to --help. When the
question about what to install was asked, the line now names the c
entry, and i with its size when installed cores were found.

install.ps1

@@ -11,7 +11,7 @@
 
     $ErrorActionPreference = "Stop"
     $defaultInstallUrl = "https://raw.githubusercontent.com/Abdess/retrobios/main/install.py"
-    $defaultInstallSha256 = "b5070145ae7920b90e8d904552a223261fae35a394552c7ce3a2b87cbcf613e8"
+    $defaultInstallSha256 = "a0b6a103d350e49f2751928c5a5560e239c52df81637a656e0691b9934e438bb"
     $maximumInstallerBytes = 2MB
     $installerExit = 0
     $installer = if ($PSScriptRoot) { Join-Path $PSScriptRoot "install.py" } else { $null }

install.py

@@ -7561,6 +7561,8 @@ def _install(args: argparse.Namespace, real_stdout: TextIO) -> None:
         # What --core resolves against, for advice that names one.
         core_choices = set(available_choices(files, omitted_files)["cores"])
         selection = _requested_narrowing(args, plat_name, files, omitted_files, manifest)
+        # What declining the size question points back at, when it was asked.
+        smaller = ""
         if (
             selection is None
             and interactive
@@ -7576,6 +7578,13 @@ def _install(args: argparse.Namespace, real_stdout: TextIO) -> None:
                 plat_name, files, omitted_files, installed,
                 display_name(plat_name, manifest),
             )
+            if selection is None:
+                smaller = ("  Nothing downloaded. To install less, run the same command "
+                           "again and type c at the first question to choose systems")
+                if installed is not None:
+                    smaller += (f", or i for only what the installed cores read "
+                                f"({format_size(_bytes(installed[0]))})")
+                smaller += "."
             if selection == INSTALLED_ONLY:
                 files, omitted_files = installed
                 print("\n  Same choice without questions: "
@@ -7752,7 +7761,9 @@ def _install(args: argparse.Namespace, real_stdout: TextIO) -> None:
                     f"\nDownload {format_size(dl_size)} to {bios_path}? [Y/n] "
                 )
             ):
-                print("  Nothing downloaded. --system, --core and --region "
+                # A beginner who just passed the c entry was sent to a
+                # 91-line --help.
+                print(smaller or "  Nothing downloaded. --system, --core and --region "
                       "install less (see --help).")
                 total_up_to_date += len(up_to_date)
                 total_declined += len(to_download)

install.sh

@@ -18,7 +18,7 @@ esac
 TEMP_INSTALLER=""
 TEMP_DIRECTORY=""
 DEFAULT_INSTALL_URL="https://raw.githubusercontent.com/Abdess/retrobios/main/install.py"
-DEFAULT_INSTALL_SHA256="b5070145ae7920b90e8d904552a223261fae35a394552c7ce3a2b87cbcf613e8"
+DEFAULT_INSTALL_SHA256="a0b6a103d350e49f2751928c5a5560e239c52df81637a656e0691b9934e438bb"
 MAX_INSTALLER_BYTES=2097152
 
 cleanup() {

tests/test_install_selection.py

@@ -354,6 +354,42 @@ class CommandLineChoices(unittest.TestCase):
                 install.parse_selection(bad, 5)
 
 
+class DecliningTheSizePointsAtTheChoice(unittest.TestCase):
+    """Saying no to `Download 8.4 GB?` printed "--system, --core and
+    --region install less (see --help)": a 91-line help for someone who had
+    just passed the c entry that does it."""
+
+    def _run(self, answers: list[str], *options: str) -> str:
+        replies = iter(answers)
+        out = io.StringIO()
+        with FakeRepository() as repo, \
+                mock.patch.object(sys, "argv", ["install.py", "--platform", "retroarch",
+                                                "--dest", str(repo.dest), *options]), \
+                mock.patch.object(install, "MANIFEST_URL",
+                                  repo.env()["RETROBIOS_BASE_URL"] + "/install/{platform}.json"), \
+                mock.patch.object(install, "RAW_FILE_URL",
+                                  repo.env()["RETROBIOS_BASE_URL"] + "/{path}"), \
+                mock.patch.object(install, "CONFIRM_FROM_BYTES", 1), \
+                mock.patch("sys.stdin", mock.Mock(isatty=lambda: True)), \
+                mock.patch("builtins.input", lambda _prompt="": next(replies)), \
+                contextlib.redirect_stdout(out):
+            try:
+                install.main()
+            except SystemExit:
+                pass
+            self.assertEqual(repo.installed(), [])
+        return out.getvalue()
+
+    def test_install_everything_then_no_names_the_c_entry(self):
+        out = self._run(["", "n"])
+        self.assertIn("type c at the first question", out)
+        self.assertNotIn("see --help", out)
+
+    def test_options_given_keep_the_option_advice(self):
+        out = self._run(["n"], "--system", "sony-playstation")
+        self.assertIn("--system, --core and --region install less", out)
+
+
 class ACoreWithNoFileOfItsOwn(unittest.TestCase):
     """pcsx_rearmed, swanstation and pcsx1 showed `0 files, 0 B` in the
     cores step and in --list-cores, which reads as "this core gets nothing":