Greg Minshall <minshall@umich.edu> writes:

> hi.  i occasionally want to switch from the org package to a git
> version, then back again.  and, i want to avoid the dread "mixed
> installation".
>
> i'm wondering is there a way people do this other than simply
> installing/deleting the package version?
>

As I understand it, the critical part is when Emacs compiles the org
files to get the *.elc versions. Provided you do not have any org
functionality loaded during that compilation process, everything should
be OK. The 'mixed' versions problem arises because you go to compile a
different version and Emacs includes definitions already loaded from
another version, generating *.elc files with mixed versions.

Once org is compiled, the critical part is having the org version you
want show up first in the load-path, so the problem becomes one of just
managing the load-path entries appropriately. You could just ensure the
version you want is higher in the load-path or you could go the
'paranoid' route and have code which removes the version you don't want
from the load-path.

In the past, what I've done is have the git version of org in a specific
directory which I build with a separate process from the command line
using the make recipes in the repository - essentially just configuring
and running make. I then have some code in my init.el file which sets
that version at the start of my load-path when I want to run it and
which I comment out when I just want to run the version installed by
package.el. I also use the use-package macro to load my org
configuration and have two different blocks for that - one loading the
git repo version and one loading the org-plus-contrib  version I
normally use. I just comment out the one I don't want to use. I probably
could write some elisp to automate this, but to be honest, I switch
between org versions so rarely, commenting/uncommenting parts of my
init.el file is easy enough.

I don't do any of that at the moment as I've not needed to run from the
git repo since I switched to spacemacs and the spacemacs setup already
has the necessary workflow to ensure new versions of org are compiled in
a clean environment. Have not yet thought about how I will need to add
git based org when using spacemacs. Suspect All I'll need to do is
adjust the load-path as part of the init to reference the git sources
before any org functionality is loaded.

--
Tim Cross