Merge branch 'maint-1.7.11' into maint

Merge branch 'maint-1.7.11' into maint

* maint-1.7.11:
  Almost 1.7.11.6
  gitweb: URL-decode $my_url/$my_uri when stripping PATH_INFO
  rebase -i: use full onto sha1 in reflog
  sh-setup: protect from exported IFS
  receive-pack: do not leak output from auto-gc to standard output
  t/t5400: demonstrate breakage caused by informational message from prune
  setup: clarify error messages for file/revisions ambiguity
  send-email: improve RFC2047 quote parsing
  fsck: detect null sha1 in tree entries
  do not write null sha1s to on-disk index
  diff: do not use null sha1 as a sentinel value