Re: [PATCH 2/2] difftool: add a feature flag for the builtin vs scripted version

Johannes Schindelin [off-list ref] writes:

Hi Junio,

On Wed, 23 Nov 2016, Junio C Hamano wrote:

quoted

Junio C Hamano [off-list ref] writes:

quoted

Can't you route the control upon seeing "git difftool" to your
experimental "C" difftool and check the configuration there?  Then
you can decide to run_command() a non-builtin one depending what the
configuration says---that way, you would incur cost of spawning Perl
only when you need it, no?

FWIW, the approach taken by 73c2779f42 ("builtin-am: implement
skeletal builtin am", 2015-08-04) is what I had in mind when I wrote
the above.

Maybe that worked back then. But I doubt it, because checking out that
revision, I get this "warning":

Makefile:1732: warning: overriding recipe for target 'git-am'
Makefile:1696: warning: ignoring old recipe for target 'git-am'

Seems like a matter of luck whether the `make` executable you happen to
use guesses what we want: to munge git-am.sh into git-am, as opposed to
hard-linking git to git-am.

You do not need to keep two copies of "git-cmd", though.  commands[]
table can have an entry "difftool" that points at cmd_difftool(),
which switches between run_command("difftool-scripted") or makes a
function call to a static difftool_builtin() that you wrote in 1/2.