Source Code Repository Conventions

[Mike Freemon <mfreemon@xxxxxxxxxxxx>]

Following up on our discussion yesterday during the developers meeting 
regarding source code repository conventions:

https://wiki.ncsa.illinois.edu/display/NDS/Source+Code+Repository+Conventions

The point has been raised since the meeting that branching is not the 
same between hg and git.

* git branch != hg branch
* git branches are more like hg bookmarks  <-- use these for lightweight 
development
* hg branches are more heavyweight and the information about them is 
baked into the commit for all time
* there should be only a very small number of long-lived hg branches in 
a hg repository

As a bit of an aside, git submodules work differently than hg 
subrepositories.  We are currently using git submodules in at least one 
of the NDS repositories.  I consider this an aside since we don't really 
need to use submodules (AFAICT).

The main issue is the branching and merging conventions we want to 
adopt.  These conventions (the language we use and the documentation we 
write) are, on a day-to-day practical level, closely associated with the 
tools we use and the terminology of those tools.  I'm certain either 
mercurial or git would work for us just fine.  It does, however, seem 
like a good idea to just pick one and go with it.

Please comment.

Various random links that touch on this topics:

* 
https://docs.python.org/devguide/gitdevs.html#main-differences-between-git-and-hg
* https://jhw.dreamwidth.org/1868.html  (pro hg)
* 
https://felipec.wordpress.com/2013/08/27/analysis-of-hg-and-git-branches/ 
(pro git)
* https://git-scm.com/book/en/v2/Git-Tools-Submodules
* https://mercurial.selenic.com/wiki/Subrepository

- Mike