Merge branch 'maint'

Merge branch 'maint'

* maint:
  Better advice on using topic branches for kernel development
  Documentation: update implicit "--no-index" behavior in "git diff"
  Documentation: expand 'git diff' SEE ALSO section
  Documentation: diff can compare blobs
  Documentation: gitrevisions is in section 7
  shell portability: no "export VAR=VAL"
  CodingGuidelines: reword parameter expansion section
  Documentation: update-index: -z applies also to --index-info
  Documentation: No argument of ALLOC_GROW should have side-effects