I want "fast forward my workdir to upstream if it's safe"

[merlyn@stonehenge.com (Randal L. Schwartz)]

For the past few years, within any given 12 hour period, at least
one person on #git would come up with the use case with which I'm
really familiar (having needed it many times myself):

  I have a workdir tracking a remote.
  I may or may not have made local edits... I can't remember.
  I may or may not have made local commits... I can't remember.
  But the upstream might now have changed... please update me *safely*.

Seriously, this comes up, a lot.  Typically, from a cron job updater,
but often just "what can I do to make sure I'm up to date".

So, what I need is a command, likely an option to "git merge" that says "do
everything that a git merge would do except abort if it would have been a
merge commit".  In other words, abort if the workdir is dirty or is not a
fast-forward update to the upstream.  Bonus if it exits non-zero if
something went wrong.

Please don't tell me "use these three commands in this script".
I want a *command* I can tell people in #git.

-- 
Randal L. Schwartz - Stonehenge Consulting Services, Inc. - +1 503 777 0095
<merlyn@stonehenge.com> <URL:http://www.stonehenge.com/merlyn/>
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