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Re: [PATCH v3 2/5] status: add --[no-]ahead-behind to status and commit for V2 format.

On 1/4/2018 5:05 PM, Junio C Hamano wrote:
Jeff Hostetler <git@xxxxxxxxxxxxxxxxx> writes:

+		sti = stat_tracking_info(branch, &nr_ahead, &nr_behind,
+					 &base, s->ahead_behind_flags);
  		if (base) {
  			base = shorten_unambiguous_ref(base, 0);
  			fprintf(s->fp, "# branch.upstream %s%c", base, eol);
  			free((char *)base);
- if (ab_info)
-				fprintf(s->fp, "# branch.ab +%d -%d%c", nr_ahead, nr_behind, eol);
+			if (sti >= 0) {
+				if (s->ahead_behind_flags == AHEAD_BEHIND_FULL)
+					fprintf(s->fp, "# branch.ab +%d -%d%c",
+						nr_ahead, nr_behind, eol);
+				else if (s->ahead_behind_flags == AHEAD_BEHIND_QUICK)
+					fprintf(s->fp, "# branch.equal %s%c",
+						sti ? "neq" : "eq", eol);

This is related to what I said in the review of [1/5], but this
arrangement to require the caller to know that _QUICK request
results in incomplete information smells like a bit of maintenance

We'd rather allow the caller to tell if it was given incomplete
information from the values returned by stat_tracking_info()
function (notice the plural "values" here; what is returned in
nr_{ahead,behind} also counts).  For example, we can keep the (-1 =>
"no relation", 0 => "identical", 1 => "different") as return values
of the function, but have it clear nr_{ahead,behind} when it only
knows the two are different but not by how many commits.  That way,
this step can instead do:

	ab_info = stat_tracking_info(...);
	if (base) {
		... do the base thing ...
		if (ab_info > 0) {
			/* different */
			if (nr_ahead || nr_behind)
				fprintf(... +%d -%d ... nr_ahead, nr_behind, ...);
				fprintf(... "neq" ...);
		} else if (!ab_info) {
			/* same */
			fprintf(... +%d -%d ... nr_ahead, nr_behind, ...);

That would allow us to later add different kinds of _QUICK that do
not give full information without having to update this consumer
with something like

-	else if (s->ahead_behind_flags == AHEAD_BEHIND_QUICK)
+	else if (s->ahead_behind_flags == AHEAD_BEHIND_QUICK ||
+		 s->ahead_behind_flags == AHEAD_BEHIND_QUICK_DIFFERENTLY)

when it happens.

Two related tangents.

  - I do not see why "eq" need to exist at all.  Even in _QUICK mode,
    when you determine that two are identical, you know your branch
    is ahead and behind by 0 commit each.

  - A short-format that is easy to parse by machines does not have to
    be cryptic to humans.  s/neq/not-equal/ or something may be an


Thanks for the review.  Let me update it along the lines suggested here.
It felt odd to define the nr_{ahead,behind} as undefined, but short of
making them negative or something I wasn't sure what was best.