Begin SubmittingPatches with a check list

It seems that some people prefer a short list to a long text. But even for
the latter group, a quick reminder list is useful. So, add a check list to
Documentation/SubmittingPatches of what to do to get your patch accepted.

Signed-off-by: Johannes Schindelin <Johannes.Schindelin@gmx.de>
Signed-off-by: Junio C Hamano <junkio@cox.net>

Documentation/SubmittingPatches

@@ -1,3 +1,30 @@
+Checklist (and a short version for the impatient):
+
+	- make commits of logical units
+	- check for unnecessary whitespace with "git diff --check"
+	  before committing
+	- do not check in commented out code or unneeded files
+	- provide a meaningful commit message
+	- the first line of the commit message should be a short
+	  description and should skip the full stop
+	- if you want your work included in git.git, add a
+	  "Signed-off-by: Your Name <your@email.com>" line to the
+	  commit message (or just use the option "-s" when
+	  committing) to confirm that you agree to the Developer's
+	  Certificate of Origin
+	- do not PGP sign your patch
+	- use "git format-patch -M" to create the patch
+	- do not attach your patch, but read in the mail
+	  body, unless you cannot teach your mailer to
+	  leave the formatting of the patch alone.
+	- be careful doing cut & paste into your mailer, not to
+	  corrupt whitespaces.
+	- provide additional information (which is unsuitable for
+	  the commit message) between the "---" and the diffstat
+	- send the patch to the list _and_ the maintainer
+
+Long version:
+
 I started reading over the SubmittingPatches document for Linux
 kernel, primarily because I wanted to have a document similar to
 it for the core GIT to make sure people understand what they are