Point rspec-rails sub-build

1. Clone rspec-rails' main branch for sub-builds

2. Trick rspec-rails' sub-builds into using 4.0.0.pre

     ============= Starting rspec-rails specs ===============
    Running specs for rspec-rails
    ~/work/rspec-mocks/rspec-rails ~/work/rspec-mocks/rspec-mocks
    Fetching gem metadata from https://rubygems.org/.........
    Fetching gem metadata from https://rubygems.org/.
    Resolving dependencies...
    Bundler could not find compatible versions for gem "rspec-core":
      In Gemfile:
        rspec-core

        rspec-rails was resolved to 4.1.0.pre, which depends on
          rspec-core (= 3.11.0.pre)

    Could not find gem 'rspec-core (= 3.11.0.pre)', which is required by gem
    'rspec-rails', in any of the relevant sources:
      source at `/home/runner/work/rspec-mocks/rspec-core`

Author: pirj

ci/.github/workflows/ci.yml

@@ -8,6 +8,8 @@ on:
   pull_request:
     branches:
       - '*'
+env:
+  RSPEC_CI: true
 jobs:
   test:
     name: Ruby ${{ matrix.ruby }} ${{ matrix.name_extra || '' }}

ci/script/clone_all_rspec_repos

@@ -9,7 +9,7 @@ if is_mri; then
   clone_repo "rspec-core"
   clone_repo "rspec-expectations"
   clone_repo "rspec-mocks"
-  clone_repo "rspec-rails"
+  clone_repo "rspec-rails" "main"
   clone_repo "rspec-support"
 
   popd

ci/script/functions.sh

@@ -16,7 +16,13 @@ fi
 
 function clone_repo {
   if [ ! -d $1 ]; then # don't clone if the dir is already there
-    travis_retry eval "git clone https://github.com/rspec/$1 --depth 1 --branch $MAINTENANCE_BRANCH"
+    if [ -z "$2" ]; then
+      BRANCH_TO_CLONE="$MAINTENANCE_BRANCH"
+    else
+      BRANCH_TO_CLONE="$2"
+    fi
+
+    travis_retry eval "git clone https://github.com/rspec/$1 --depth 1 --branch $BRANCH_TO_CLONE"
   fi;
 }