reorganize section on producing patches with Mercurial

[sagetrac-mvngu]

From Mariah Lenox on this sage-support thread:

> Tutorials, tips and techniques on making and managing patches should
> go in the Developers' Guide at
>
> http://www.sagemath.org/doc/developer/

Aha!  This already has the stuff I was going to write up.

The reason that I never looked at this is that I do not consider
myself
a "developer".  I found the Sage documentation for sxrange/xsrange
confusing,
William suggested I write a patch for the documentation, and I tried
to do so.

The section that you referenced "Producing Patches with Mercurial" is
in the second half of the Developers' Guide.  I never would have found
it without your pointing me at it.

I respectfully suggest that this section be split out to a "How to
make
a Sage patch (for newbies)" ... or at the very least moved to the
beginning
of the Developers' Guide.

CC: @sagetrac-mariah

Component: documentation

Issue created by migration from https://trac.sagemath.org/ticket/6987

[sagetrac-mvngu]

comment:2

Closing this as fixed by #8108 and #8147.