Re: Feature request: a merge strategy that makes any file difference a merge conflict

[Junio C Hamano <gitster@pobox.com>]

Michael Ernst <mernst@cs.washington.edu> writes:

> Git's built-in merge strategies, such as ort, sometimes create a
> clean-but-incorrect merge.  A merge driver or a mergetool cannot be
> used to correct such problems, because a merge driver or mergetool is
> only called when the strategy resulted in a conflict (so far as I
> understand).

A custom low-level merge driver is always called when selected via
the attribute mechansism (see how merge-ll.c:ll_merge() calls
find_ll_merge_driver()) and participates in a content-level 3-way
merge.

If you are trying to interfere with cases that a content-level 3-way
merge does not kick in (e.g., your side did not change anything in
the file since their history forked, and they modified the file; the
tree level 3-way merge will resolve it to take their version), then
it is true that the low-level merge driver is not invoked, but I
somehow get an impression from the above description that it is not
what you are trying to do.

> It is challenging to write a merge strategy, but it is
> much easier to write a merge driver or a mergetool.

A merge strategy is about performing three-way merge at the tree
level, figuring out which three variants of contents to hand to a
merge driver that handles the content-level three-way merge.  They
serve totally different purposes and comparing them is like
comparing apples and oranges.