Teach "--gpg-sign" option to many commands that create commits.

* bc/gpg-sign-everywhere:
  pull: add the --gpg-sign option.
  rebase: add the --gpg-sign option
  rebase: parse options in stuck-long mode
  rebase: don't try to match -M option
  rebase: remove useless arguments check
  am: add the --gpg-sign option
  am: parse options in stuck-long mode
  git-sh-setup.sh: add variable to use the stuck-long mode
  cherry-pick, revert: add the --gpg-sign option

"git pull" learned to pay attention to pull.ff configuration
variable.

* da/pull-ff-configuration:
  pull: add --ff-only to the help text
  pull: add pull.ff configuration

git merge already allows us to sign commits, and git rebase has recently
learned how to do so as well.  Teach git pull to parse the -S/--gpg-sign
option and pass this along to merge or rebase, as appropriate.

Signed-off-by: brian m. carlson <sandals@crustytoothpaste.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

Finishing touches so that an expected error message will not leak to
the UI.

* jk/pull-rebase-using-fork-point:
  pull: suppress error when no remoteref is found

Commit 48059e4 (pull: use merge-base --fork-point when appropriate,
2013-12-08) incorrectly assumes that get_remote_merge_branch will either
yield a non-empty string or return an error, but there are circumstances
where it will yield an empty string.

The previous code then invoked git-rev-list with no arguments, which
results in an error suppressed by redirecting stderr to /dev/null.  Now
we invoke git-merge-base with an empty branch name, which also results
in an error.  Suppress this in the same way.

Signed-off-by: John Keeping <john@keeping.me.uk>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

Signed-off-by: David Aguilar <davvid@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

Add a `pull.ff` configuration option that is analogous
to the `merge.ff` option.

This allows us to control the fast-forward behavior for
pull-initiated merges only.

Signed-off-by: David Aguilar <davvid@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

* jk/pull-rebase-using-fork-point:
  rebase: use reflog to find common base with upstream
  pull: use merge-base --fork-point when appropriate

Since commit d96855f (merge-base: teach "--fork-point" mode, 2013-10-23)
we can replace a shell loop in git-pull with a single call to
git-merge-base.  So let's do so.

Signed-off-by: John Keeping <john@keeping.me.uk>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

Previously, fetch's "--tags" option was considered equivalent to
specifying the refspec "refs/tags/*:refs/tags/*" on the command line;
in particular, it caused the remote.<name>.refspec configuration to be
ignored.

But it is not very useful to fetch tags without also fetching other
references, whereas it *is* quite useful to be able to fetch tags *in
addition to* other references.  So change the semantics of this option
to do the latter.

If a user wants to fetch *only* tags, then it is still possible to
specifying an explicit refspec:

    git fetch <remote> 'refs/tags/*:refs/tags/*'

Please note that the documentation prior to 1.8.0.3 was ambiguous
about this aspect of "fetch --tags" behavior.  Commit

    f0cb2f137c 2012-12-14 fetch --tags: clarify documentation

made the documentation match the old behavior.  This commit changes
the documentation to match the new behavior.

Signed-off-by: Michael Haggerty <mhagger@alum.mit.edu>
Signed-off-by: Junio C Hamano <gitster@pobox.com>