Re: [PATCH v2 1/3] commit: reword the empty-commit rebase errors

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

Junio C Hamano <gitster@pobox.com> writes:

>> +			die(_("cannot do a partial commit while resolving a commit that became empty."));
>
> That is a mouthful.  It also is awkward to say "while resolving a commit".

This still stands, but I haven't come up with a better alternative yet.

> More importantly, I am not sure if whence == FROM_REBASE_PICK at
> this point in the code flow is a sufficient sign to tell that we
> were not just in the middle of a rebase, not just a rebase stopped
> with _some_ conflict, but the way the rebase stopped was because a
> step in rebase resulted in a commit that is no-op relative to the
> previous commit.  What makes us certain that the rebase-pick is
> empty?

This confusion was because FROM_REBASE_PICK is a misleading name.

sequencer_determine_whence() is the only place that declares the
whence is FROM_REBASE_PICK, and it specifically checks if the
rebase-head and cherry-pick-head are identical before yielding that
value, so by definition we are dealing with an empty-pick situation.

This came from 430b75f720 (commit: give correct advice for empty
commit during a rebase, 2019-12-06); interestingly, the name of
FROM_REBASE_PICK and is_from_rebase() seem to have confused even the
originating commit ;-)  The lines in question

+               else if (is_from_rebase(whence))
+                       die(_("cannot do a partial commit during a rebase."));

are from that commit, which wanted to "give correct advice for empty
commit during a rebase".

We may want to

 * change the code that does whence == FROM_REBASE_PICK to use
   is_from_rebase(whence) everywhere (other than the implementation
   of is_from_rebase() itself, of course).

 * give FROM_REBASE_PICK and is_from_rebase() better names that
   contain "empty" somewhere.

to unconfuse me.