Re: [PATCH v3 3/3] diff: define block by number of non-space chars

From: Junio C Hamano <gitster@pobox.com>
Date: Aug 15, 2017, 19:54 UTC
Message-ID: <xmqqy3qkppxt.fsf@gitster.mtv.corp.google.com>
In-Reply-To: <41a7ff674072559415f98b81ffde798d94aed2fc.1502754962.git.jonathantanmy@google.com>

Jonathan Tan <jonathantanmy@google.com> writes:

Show 12 quoted lines

> The existing behavior of diff --color-moved=zebra does not define the
> minimum size of a block at all, instead relying on a heuristic applied
> later to filter out sets of adjacent moved lines that are shorter than 3
> lines long. This can be confusing, because a block could thus be colored
> as moved at the source but not at the destination (or vice versa),
> depending on its neighbors.
>
> Instead, teach diff that the minimum size of a block is 10
> non-whitespace characters. This allows diff to still exclude
> uninteresting lines appearing on their own (such as those solely
> consisting of one or a few closing braces), as was the intention of the
> adjacent-moved-line heuristic.

I recall that there is a logic backed by a similar rationale in blame.c::blame_entry_score() but over there we count alnum, not !isspace, to judge if a block has been split into too small a piece to be significant. I do not know which one is better, but if there is no strong reason, perhaps we want to unify the two, so that we can improve both heuristics at the same time?