location: prevent creating a database in a non-database file

by refusing to use the current directory if no LevelDB database exists already
unless the path is passed explicitly

Author: maxlath

lib/location.js

@@ -4,9 +4,28 @@
  * tries to find the location of the database.
  *
  */
+
 module.exports = function (argv) {
 
   var location = typeof argv.location === 'string';
-  argv.path = location && argv.location || argv._[0] || process.cwd();
+  argv.path = location && argv.location || argv._[0];
+  if (!argv.path) {
+    if (cwdIsADatabase()) {
+      argv.path = process.cwd();
+    }
+    else {
+      console.error('no database found');
+      return process.exit(1);
+    };
+  };
+};
+
+function cwdIsADatabase () {
+  try {
+    var CURRENT = require('fs').readFileSync('./CURRENT').toString();
+    return CURRENT.split('-')[0] === 'MANIFEST';
+  } catch (err) {
+    return false;
+  };
 };