bug#13405: 24.3; log-view-diff-changeset reports wrong results

bug#13405: 24.3; log-view-diff-changeset reports wrong results

[Andy Moreton]

Emacs trunk built from r111470 on Windows XP (with mingw gcc 4.7.2).

Using vc support in emacs with a mercurial (hg) repository:
1) Annotate a file under hg version control.
2) Type "l" (vc-annotate-show-log-revision-at-line) in the annotate buffer
    to show the *vc-change-log* buffer containing the log entry for
    revision 46769.
3) In the *vc-change-log* buffer, type D (log-view-diff-changeset) to view
    the changeset for that single revision.
    Emacs runs "hg diff --git -r 46768 -r 46769", but this does not show
    the expected contents of the changeset, as the previous revision was
    on a different named branch. Instead this shows the (large) diff between
    the two branches. The line counts illustrate this:

    # hg diff -r 46768 -r 46769 | wc -l   ## Diff between branches
    102276
    # hg diff -c 46769 | wc -l            ## Changeset diff
    295
    # hg log -p -r 46769 | wc -l          ## Changeset diff + hg metadata
    302

    The second and third commands give the expected output.
    Can log-view-diff-changeset be changed to deal with this case more
    gracefully ?

        AndyM

bug#13405: 24.3; log-view-diff-changeset reports wrong results

[Stefan Monnier]

> 3) In the *vc-change-log* buffer, type D (log-view-diff-changeset) to view
>    the changeset for that single revision.
>    Emacs runs "hg diff --git -r 46768 -r 46769", but this does not show
>    the expected contents of the changeset, as the previous revision was
>    on a different named branch. Instead this shows the (large) diff between
>    the two branches. The line counts illustrate this:

>    # hg diff -r 46768 -r 46769 | wc -l   ## Diff between branches
>    102276
>    # hg diff -c 46769 | wc -l            ## Changeset diff
>    295
>    # hg log -p -r 46769 | wc -l          ## Changeset diff + hg metadata
>    302

>    The second and third commands give the expected output.
>    Can log-view-diff-changeset be changed to deal with this case more
>    gracefully ?

VC assumes you can get the changeset by running
"hg diff -r <something> -r 46769".  Is there a <something> that would
give the right answer?  Ideally this <something> should be computable
from "46769".


        Stefan

bug#13405: 24.3; log-view-diff-changeset reports wrong results

[Andy Moreton]

On 11/01/2013 23:13, Stefan Monnier wrote:
>> 3) In the *vc-change-log* buffer, type D (log-view-diff-changeset) to view
>>     the changeset for that single revision.
>>     Emacs runs "hg diff --git -r 46768 -r 46769", but this does not show
>>     the expected contents of the changeset, as the previous revision was
>>     on a different named branch. Instead this shows the (large) diff between
>>     the two branches. The line counts illustrate this:
>
>>     # hg diff -r 46768 -r 46769 | wc -l   ## Diff between branches
>>     102276
>>     # hg diff -c 46769 | wc -l            ## Changeset diff
>>     295
>>     # hg log -p -r 46769 | wc -l          ## Changeset diff + hg metadata
>>     302
>
>>     The second and third commands give the expected output.
>>     Can log-view-diff-changeset be changed to deal with this case more
>>     gracefully ?
>
> VC assumes you can get the changeset by running
> "hg diff -r <something> -r 46769".  Is there a <something> that would
> give the right answer?  Ideally this <something> should be computable
> from "46769".

This can be done using revsets:
# hg diff -r46769^1 -r 46769 | wc -l
295

However that relies on having a new enough version of mercurial that 
supports the revsets syntax. The "hg diff -c" or "hg log -p" commands 
work with older mercurial versions that do not support revset syntax.

     AndyM