Merge remote-tracking branch 'github/master' into git-po-master

Merge remote-tracking branch 'github/master' into git-po-master

* github/master: (42 commits)
  Git 2.30-rc1
  git-gui: use gray background for inactive text widgets
  Another batch before 2.30-rc1
  git-gui: Fix selected text colors
  Makefile: conditionally include GIT-VERSION-FILE
  git-gui: fix colored label backgrounds when using themed widgets
  config.mak.uname: remove old NonStop compatibility settings
  diff: correct interaction between --exit-code and -I<pattern>
  t/perf: fix test_export() failure with BSD `sed`
  style: do not "break" in switch() after "return"
  compat-util: pretend that stub setitimer() always succeeds
  strmap: make callers of strmap_remove() to call it in void context
  doc: mention Python 3.x supports
  index-format.txt: document v2 format of file system monitor extension
  docs: multi-pack-index: remove note about future 'verify' work
  init: provide useful advice about init.defaultBranch
  get_default_branch_name(): prepare for showing some advice
  branch -m: allow renaming a yet-unborn branch
  init: document `init.defaultBranch` better
  t7900: use --fixed-value in git-maintenance tests
  ...