tools/test: Prepare to add a suite that doesn't run by default

Currently, all suites run by default, so the only functional change
is the changed usage-message text.

tools/test

@@ -28,8 +28,9 @@ usage: tools/test [OPTION]... [SUITE]...
 
 Run our tests.
 
-By default, run all suites, but only on files changed in this branch
-as found by \`tools/git changed-files \$(tools/git base)\`.
+By default, run all suites except any noted under "Suites:" below, but only
+on files changed in this branch as found by
+\`tools/git changed-files \$(tools/git base)\`.
 
 What tests to run:
   --all-files
@@ -48,8 +49,9 @@ What tests to run:
               run Jest tests on only one platform (iOS). This is
               usually fine, because the vast majority of our Jest
               tests don't depend meaningfully on the platform.
-  --all       In the given suites, run all tests on all files. Same as
-              --all-files --platform both.
+  --all       In the given suites, run all tests on all files, equivalently
+              to \`--all-files --platform both\`. If no list of suites was
+              specified, run all suites.
 
 Extra things to do:
   --coverage  Collect test-coverage information.  Only meaningful
@@ -68,10 +70,19 @@ EOF
     exit 2
 }
 
+# The complete list of suites.
+all_suites=(native flow lint jest prettier deps tsflower)
+
 opt_coverage=
 opt_files=branch
 opt_platform=sloppy
 opt_fix=
+
+# The suites to run if none are given as arguments. Unless --all is
+# specified, this doesn't have to be the complete list; just be sure to
+# document in the usage message when a suite gets skipped.
+opt_default_suites=(native flow lint jest prettier deps tsflower)
+
 opt_suites=()
 while (( $# )); do
     case "$1" in
@@ -86,7 +97,7 @@ while (( $# )); do
             esac
             shift
             ;;
-        --all) opt_files=all; opt_platform=both; shift;;
+        --all) opt_files=all; opt_platform=both; opt_default_suites=( "${all_suites[@]}" ); shift;;
         --fix) opt_fix=1; shift;;
         native|flow|lint|jest|prettier|deps|tsflower)
             opt_suites+=("$1"); shift;;
@@ -95,9 +106,7 @@ while (( $# )); do
 done
 
 if [ -z "$opt_suites" ]; then
-    # This default doesn't have to be the complete list; just be sure to
-    # document in the usage message any suites that it skips.
-    opt_suites=(native flow lint jest prettier deps tsflower)
+    opt_suites=( "${opt_default_suites[@]}" )
 fi
 
 files_base_commit=