Merge branch '1.8' into 5421_warning_for_autodoc_default_flags

CHANGES

@@ -16,6 +16,7 @@ Features added
 Bugs fixed
 ----------
 
+* #5418: Incorrect default path for sphinx-build -d/doctrees files
 * #5421: autodoc emits deprecation warning for :confval:`autodoc_default_flags`
 
 Testing

sphinx/cmd/build.py

@@ -219,7 +219,7 @@ def build_main(argv=sys.argv[1:]):  # type: ignore
         args.confdir = args.sourcedir
 
     if not args.doctreedir:
-        args.doctreedir = os.path.join(args.sourcedir, '.doctrees')
+        args.doctreedir = os.path.join(args.outputdir, '.doctrees')
 
     # handle remaining filename arguments
     filenames = args.filenames