Merge pull request #358 from tp-m/no-args

Try harder to infer build and source directories if called without arguments.

mesonbuild/mesonmain.py

@@ -231,10 +231,17 @@ def run(mainfile, args):
         return 0
     args = options.directories
     if len(args) == 0 or len(args) > 2:
+        # if there's a meson.build in the dir above, and not in the current
+        # directory, assume we're in the build directory
+        if len(args) == 0 and not os.path.exists('meson.build') and os.path.exists('../meson.build'):
+            dir1 = '..'
+            dir2 = '.'
+        else:
             print('{} <source directory> <build directory>'.format(sys.argv[0]))
             print('If you omit either directory, the current directory is substituted.')
             print('Run {} --help for more information.'.format(sys.argv[0]))
             return 1
+    else:
         dir1 = args[0]
         if len(args) > 1:
             dir2 = args[1]