Pete Harlan [off-list ref] writes:

On 01/10/2012 10:59 PM, Junio C Hamano wrote:

quoted

There may be existing scripts that leave the standard input and the
standard output of the "git merge" connected to whatever environment the
scripts were started, and such invocation might trigger the above
"interactive session" heuristics. Such scripts can export GIT_MERGE_LEGACY
environment variable set to "yes" to force the traditional behaviour.

The name GIT_MERGE_LEGACY gives no clue about what flavor of legacy
merge behavior is being enabled.  Something like GIT_MERGE_LEGACY_EDIT
might be clearer, or perhaps just have GIT_MERGE_EDIT=0 to get the old
behavior without reference to whether or not that behavior is
considered legacy.

Hrm.

The only case your suggestion may make a difference would be when we find
another earlier UI mistake we would want to correct in a backward
incompatible way that affects _existing_ scripts.

With your suggestion, they need to export "GIT_MERGE_EDIT=0" today, and
they will need to update again to export "GIT_MERGE_SOMETHINGELSE=0" when
such an incompatible change comes.

With a single "GIT_MERGE_LEGACY=YesPlease", they can be future-proofed today
and will not be affected when we make another incompatible change.

So I am not sure why separating the big-red-switch into smaller pieces
would be an improvement, especially wnen the scripts that want to specify
finer-grained control of features can use "--[no-]edit" options to
explicitly ask for it.