bug#19319: ? Unexpected behavior in diff(1)

[Todd Shandelman]

Thanks.

Well, I must say that is all rather counter-intuitive.

I never dreamed that the amount of context I select would actually affect the diff itself and how it is computed.

But if you say so, I guess that is how it works.

Todd

On 8 December 2014 at 16:46, Eric Blake <address@hidden> wrote:

On 12/08/2014 03:27 PM, Todd Shandelman wrote:
> With -U1 and -U2 , the --ignore-matching-lines='Id' argument suppresses
> display of the difference between the 'Id' lines, as expected.

At that (small) level of context, the hunk containing the 'Id' line is
separate from the remaining hunks, so the hunk is omitted.

>
> But with -U3, the diff of the 'Id' lines reappears,  in spite of the
> --ignore-matching-lines='Id'
> argument.
>
> Why is that?

As soon as you have enough context, the hunk for the 'Id' line is the
SAME hunk as the rest of the changes.  --ignore-matching-lines omits a
hunk only if the entire hunk matches the regex; but as soon as you have
other changes, then the entire hunk is output verbatim.

--ignore-matching-lines does NOT ignore individual lines within a hunk,
but only a hunk at a time.

--
Eric Blake   eblake redhat com    +1-919-301-3266
Libvirt virtualization library http://libvirt.org