Merge branch 'maint'

Merge branch 'maint'

* maint:
  Document accumulated fixes since 1.7.9.2
  Git 1.7.8.5
  grep -P: Fix matching ^ and $
  am: don't infloop for an empty input file
  rebase -m: only call "notes copy" when rewritten exists and is non-empty
  git-p4: remove bash-ism in t9800
  git-p4: remove bash-ism in t9809
  git-p4: fix submit regression with clientSpec and subdir clone
  git-p4: set useClientSpec variable on initial clone
  Makefile: add thread-utils.h to LIB_H

Conflicts:
	RelNotes
	t/t9809-git-p4-client-view.sh