Re: [PATCH] Documentation/merge-options: clarify --squash behavior

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

Vishal Verma <vishal.l.verma@intel.com> writes:

> Add a note to the --squash option for git-merge to clarify its behavior
> with respect to --commit. When --squash is supplied, 'option_commit' is
> silently dropped. This can be surprising to a user who tries to override
> the no-commit behavior of squash using --commit explicitly.
>
> Signed-off-by: Vishal Verma <vishal.l.verma@intel.com>
> ---
>
> There may be an argument to make --commit 'just work' with squash, but
> that might involve changing option_commit from OPT_BOOL to something
> that can distinguish between the default, what's requested on the
> command line, or the --no- version.

I think it is bad to silently ignore the option.  With or without
this documentation update, I think it is sensible to update the code
so that it errors out when "--squash --commit" are both given at the
same time, just like when "--squash --no-ff" is given.

Or make it "just work" as you said.  Using a boolean variable as
tristate is something we do in many places and it by itself is not a
rocket science.  You initialize the variable to -1 (unset), let
parse_options() to set it to 0/1 when "--[no-]commit" is seen, and
inspect after parse_options() finishes.  If the variable is still
-1, you know the user wants "the default" behaviour.

The "default" behaviour you are proposing would probably be
something like

        if (option_commit < 0) {
                /* 
                 * default to record the result in a commit.
                 * but --squash traditionally does not.
                 */
                if (!squash)
                        option_commit = 1;
                else
                        option_commit = 0;
        }

But I suspect that the option parsing part is the least difficult in
the "make it just work" change.  That is because I think that the
machinery to record the result in a commit is not expecting to be
asked to create a single-parent commit to record the result of the
squashing, so there may be need for adjusting to how the result
wants to be recorded before the code makes a commit.