Merge branch 'dw/signoff-doc' into maint

The documentation has been updated to hint the connection between
the '--signoff' option and DCO.

* dw/signoff-doc:
Expand documentation describing --signoff

diff --combined Documentation/git-format-patch.txt
index e3cdaeb9586017aa86aa15fec8a13371993906e3,96b52bde913b3b8a8c430cbafdc26c74ad4493a5..b149e09065a11ecf21f166261d12cfb585f3cc50
--- 1/Documentation/git-format-patch.txt
--- 2/Documentation/git-format-patch.txt
+++ b/Documentation/git-format-patch.txt
@@@ -109,6 -109,7 +109,7 @@@ include::diff-options.txt[
  --signoff::
        Add `Signed-off-by:` line to the commit message, using
        the committer identity of yourself.
+       See the signoff option in linkgit:git-commit[1] for more information.
  
  --stdout::
        Print all commits to the standard output in mbox format,
@@@ -256,10 -257,6 +257,10 @@@ you can use `--suffix=-patch` to get `0
        using this option cannot be applied properly, but they are
        still useful for code review.
  
 +--zero-commit::
 +  Output an all-zero hash in each patch's From header instead
 +  of the hash of the commit.
 +
  --root::
        Treat the revision argument as a <revision range>, even if it
        is just a single commit (that would normally be treated as a