Merge branch 'maint-1.7.7' into maint

* maint-1.7.7:
  am: don't persist keepcr flag
  mingw: give waitpid the correct signature
  git symbolic-ref: documentation fix

diff --cc compat/mingw.c
Simple merge

diff --cc compat/mingw.h
Simple merge

diff --cc git-am.sh
Simple merge