when merged more files are listed as changed

[Prabhakar S]

Thank you Simon. Your explanation did help me.

However, I have few more questions.

We are having two repos forked from a base repo. And these two repos am
going to call as branch1 and branch2. We are periodically pullying from
branch2 -> branch1

And if you consider the graph below.

The diff for the commit of change:100 should be from the hg diff -r 97 -r
tip

tip is 100 and the diff to the next changeset is , the next merge point
what has been merged which is 98. And the 97 actually contributed to 98 and
hence I understand the diff is from

hg diff -r 97 -1 100 and this is from the branch1 perspective, as we merge
only from branch2 to branch1.( cross pull)

However, the diff should only show changes of few files which changed
between the two snapshots one is 100 and one is the 97 snapshot. It really
cannot show many changes.

And between changeset 95 and 97 there are lesser changes. Since already
changeset :96 is already there as a result of merge. The diff simply cannot
show changes beyond changeset:96

Help me to interpret the diff correctly. But, I believe as it is not
breaking anything, it is doing correct things, but what it shows of as the
diff during merge sometimes is actually more than the files changed. This I
have seen to occur sometimes and not always.

@     changeset:100 [ changeset in branch1 ]
|\
| |
| |
| |
| |
| o  changeset:99 [ changeset in branch 2 ]
| |
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o | changeset:98 [ changeset in branch1 , contributed by merge ]
|\|
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| |
| |
| |
| |
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| o changeset:97 [ changeset in branch 2 ]
| |
| |
| |
| |
| |
| |
| |
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o | changeset:96 [ Changeset in branch 1 , contributed by merge ]
|\|
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| o changeset:95 [ changeset in branch 2]
| |


Regards,
S.Prabhakar

On Thu, Jun 4, 2015 at 2:27 PM, Simon King <simon at simonking.org.uk> wrote:

> On Thu, Jun 4, 2015 at 6:49 AM, Prabhakar S <prabhakar.s at tegile.com>
> wrote:
> > On Wed, Jun 3, 2015 at 11:08 PM, Matt Mackall <mpm at selenic.com> wrote:
> >>
> >> On Wed, 2015-06-03 at 18:44 +0530, Prabhakar S wrote:
> >> > Greetings,
> >> >
> >> > We have a scenario where for two releases we are having two repos and
> >> > sometimes when the two repos are merged, say repo_REL1 is merged to
> >> > repo_REL2 and for some conflicts with two or three files .
> >> >
> >> > Once they are resolved and pushed, the notification email from hg
> shows
> >> > ,
> >> > more number of files as changed than expected.
> >> >
> >> > When i checked that , looks like it is generated using command below
> >> >
> >> > hg diff -r <tip> -r <priortotip_notsure_ifitisexact prior_to_tip> |
> >> > diffstat
> >>
> >> By default, it's going to show the difference between a commit and its
> >> first parent.
> >>
> >> > Now the question is
> >> >
> >> > 1. Is the hg notification using the above approach to send the list of
> >> > modified files ?
> >>
> >> Roughly.
> >>
> >> > 2. Why is it showing more files as modified though only few files are
> >> > modified ?
> >>
> >> If, for instance, you merge your development branch into your release
> >> branch with no conflicts.. the diff is still going to show _all your
> >> development_ because all those files have changed.
> >>
> >
> > Thank you for the details.
> >
> > When I checked that, yes according to the information above, when i run a
> > diff between the tip revision and the first parten it shows lot files in
> the
> > diffstat.
> >
> > What Iam not able to understand is, when I run 'hg diff -c
> <first_parent> ,
> > then only one file shows up, however when the diff is run between the tip
> > and the first_parent lot of files are shown up.
>
> "hg diff -c <first_parent>" means "show me the diffs that were
> introduced in <first_parent>". That has no relevance at all to the
> diffs introduced by the merge.
>
> Imagine this graph:
>
> 1-2-3-6
>  \   /
>   4-5
>
> 1 is the common ancestor. 2 and 3 were changes made on the first
> branch, and 4 and 5 were made on the second branch. 6 is the merge
> revision, so 3 is the first parent of the merge, and 5 is the second
> parent. "hg diff -c 3" will show you the diffs between 2 and 3, which
> is probably not what you were looking for.
>
>
> >
> > I understand that , if say 10 files are modified in a changeset_A and if
> it
> > is merged to a release repo, and if no conflicts also, all those 10 files
> > are going to be shown as modified.
> >
> > It would be great, if you give some good pointers to understand how this
> is
> > handled.
> >
>
> Don't think of a revision as a set of changes - think of it as a new
> snapshot of the entire state of the repository. When you use "hg
> diff", you are asking for the differences between 2 snapshots. A merge
> is just another snapshot.
>
> The diffs introduced by a merge depend on your point of view. If you
> were previously looking at the first parent, it would appear that the
> merge had introduced all the changes from the second parent's branch.
> However, from the second parent's point of view, it appears that all
> the changes from the *first* parent's branch have suddenly appeared.
>
> In terms of the graph above, the diffs from 3 to 6 would show all the
> changes that had been merged in from 4 and 5. But the diffs from 5 to
> 6 would show all the changes from 2 and 3.
>
> Does that help at all?
>
> Simon
>
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