feat(migrations) adds --force flag

Adds a `--force` flag which allows for re-running the `up`
migrations in between release candidate releases. This is
a stopgap measure due to the absence of separate migration
files in the previous release candidates of Kong 1.0, which
should allow databases built with previous release candidates
to be upgraded to the latest one.

kong/cmd/migrations.lua

@@ -29,6 +29,9 @@ Options:
 
  -q,--quiet                         Suppress all output.
 
+ -f,--force                         Run migrations even if database reports
+                                    as already executed.
+
  --db-timeout     (default 60)      Timeout, in seconds, for all database
                                     operations (including schema consensus for
                                     Cassandra).
@@ -131,11 +134,15 @@ local function execute(args)
   elseif args.command == "up" then
     migrations_utils.up(schema_state, db, {
       ttl = args.lock_timeout,
+      force = args.force,
       abort = true, -- exit the mutex if another node acquired it
     })
 
   elseif args.command == "finish" then
-    migrations_utils.finish(schema_state, db, args.lock_timeout)
+    migrations_utils.finish(schema_state, db, {
+      ttl = args.lock_timeout,
+      force = args.force,
+    })
 
   else
     error("unreachable")

kong/cmd/utils/migrations.lua

@@ -116,7 +116,7 @@ local function up(schema_state, db, opts)
 
     else
       -- fresh install: must bootstrap (which will run migrations up)
-      error("can't run migrations: database needs bootstrapping; " ..
+      error("cannot run migrations: database needs bootstrapping; " ..
             "run 'kong migrations bootstrap'")
     end
   end
@@ -128,8 +128,19 @@ local function up(schema_state, db, opts)
       error("database has pending migrations; run 'kong migrations finish'")
     end
 
+    if opts.force then
+      log.debug("forcing re-execution of these migrations:\n%s",
+                schema_state.executed_migrations)
+
+      assert(db:run_migrations(schema_state.executed_migrations, {
+        run_up = true,
+      }))
+    end
+
     if not schema_state.new_migrations then
-      log("database is already up-to-date")
+      if not opts.force then
+        log("database is already up-to-date")
+      end
       return
     end
 
@@ -151,16 +162,18 @@ local function up(schema_state, db, opts)
 end
 
 
-local function finish(schema_state, db, ttl)
+local function finish(schema_state, db, opts)
   if schema_state.needs_bootstrap then
-    log("can't run migrations: database not bootstrapped")
+    log("cannot run migrations: database not bootstrapped")
     return
   end
 
-  local opts = {
-    ttl = ttl,
-    no_wait = true, -- exit the mutex if another node acquired it
-  }
+  if opts.force then
+    log("cannot use --force with 'finish'")
+    return
+  end
+
+  opts.no_wait = true -- exit the mutex if another node acquired it
 
   local ok, err = db:cluster_mutex(MIGRATIONS_MUTEX_KEY, opts, function()
     local schema_state = assert(db:schema_state())