Re: Antw: [EXT] Re: Help understanding unexpected diff output

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

"Ulrich Windl" <Ulrich.Windl@rz.uni-regensburg.de> writes:

>> I would imagine that the answer would still be a very similar looking
>> 
>>     ‑‑‑ a/0/...
>>     +++ b/0/...
>>     @@ ‑5,12 +5,6 @@
>>      olcDatabase: {1}hdb
>>      olcDbDirectory: /var/lib/ldap
>>      olcSuffix: dc=... 
>>     ‑olcAccess: {0} ...
>>     ‑olcAccess: {1} ...
>>     ‑olcAccess: {2} ...
>>     ‑olcAccess: {3} ...
>>     ‑olcAccess: {4} ...
>>     ‑olcAccess: {5} ...
>>     olcLimits: {0}dn.exact=....
>>      olcRootDn: cn=Admin,dc=...
>>      olcRootPW: {SSHA}yZ...
>>     @@ ‑52,6 +46,12 @@
>>      entryUUID: ...
>>      creatorsName: cn=config
>>      createTimestamp: ...
>>     ‑entryCSN: ...
>>     +olcAccess: {0} ...
>>     +olcAccess: {1} ...
>>     +olcAccess: {2} ...
>>     +olcAccess: {3} ...
>>     +olcAccess: {4} ...
>>     +olcAccess: {5} ...
>>     +entryCSN: ...
>>      modifiersName: cn=config
>>     ‑modifyTimestamp: ...
>>     +modifyTimestamp: ...
>> 
>> with identical "olcAccess: {$n}" lines removed from earlier part the
>> file and added to the end of the file.
>> 
>> So I am not sure what you are asking.  It would not be correct to show
>> something like
>
> According to my eyes (just using Emacs to make sure) those olcAccess lines
> "numbered" 0 to 3, and 5 should be "context lines" as they are not changed.

And the "slightly different" example I asked you about has {4} in
both blocks identical, you are arguing that these 6 lines all should
appear as context?

It certainly is possible but then the patch would look quite
different.  As "olcAccess: {0}" line in the preimage (i.e. a/)
appears at line 8, but that same line appears in the postimage
(i.e. b/) at line 49, such a patch that match these two olcAccess
blocks as unchanged MUST delete many lines that come after
"olcAccess: {5}" in the preimage (i.e. starting at line 14 with
olcLimits, line ending at entryCSN: at line 55 must be removed,
because they used to appear immediately after "olcAccess: {5}" in
the preimage a/, but in the postimage b/, none of tme appear after
the "olcAccess: {5}" that you claim to be common and unchanged (in
the postimage, instead you have only four lines that has"entryCSN:",
"modiferName", etc. before the end of the file).

Of course, these lines in the line range 14-55 actually are the ones
that did not change, as we can see above, so if you insist that you
must keep the 6-line "olcAccess" block as common and unchanged,
because your desired patch is deleting them from the pre-image after
"olcAccess: {5}" line, your desired patch must be adding them back
to the postimage somewhere (namely, before "olcAccess: {0}" line).

Such a patch is also a valid one in that it expresses the difference
between a/ and b/ in terms of a sequence of "delete these lines from
here" and "insert these lines to here", but it would be far less
interesting than what we see above.  Instead of "we deleted 6 lines
near the beginning of the file" plus "then added 6 lines near the
end--ah, these 6 lines by the way are identical", you would instead
say "we deleted the block of lines 14-55 that appear immediately
after olcAccess:{5}" plus "we inserted the identical block of lines
immediately before olcAccess{0}".  And you'd complain in the
opposite way: "These lines are identical but appear in different
locations in the preimage and the postimage -- why aren't they shown
as context lines?"