Re: [PATCH v3 1/2] difftool: add a skeleton for the upcoming builtin

On Fri, Nov 25, 2016 at 06:41:23PM +0100, Johannes Schindelin wrote:

quoted

Ah, I didn't realize that was a requirement. If this is going to be part
of a release and real end-users are going to see it, that does make me
think the config option is the better path (than the presence of some
file), as it's our standard way of tweaking run-time behavior.

So how do you easily switch back and forth between testing the old vs the
new difftool via the test suite?

If it's for a specific tool, I'd consider teaching the test suite to run
the whole script twice: once with the flag set and once without.

That is sometimes more complicated, though, if the script creates many
sub-repos. An environment variable might be more natural. If you already
support flipping the default via config, you can probably do:

  GIT_CONFIG_PARAMETERS="'difftool.usebuiltin=true'"
  export GIT_CONFIG_PARAMETERS

-Peff