Issue with merge commit

[mani chandel]

Hi,

I am facing an issue with the merge commit.
I merged one commit into another using below commands:

$ git checkout <commit1>
$ git merge <commit2>
Now when I push this to gerrit, I see that there 2 files are modified.
Out of which 1 file has lot of duplicate code added to it.
So if I look at the diff view between base and Patchset 1 for that file, I see something like as shown below:
 
                 Base                                               Patch Set 1
-----------------------------------------------------------|--------------------------------
<<<<<<< HEAD   (350f13 commit1)       |
                                                           |  <over here there is lot of duplicate
=======                                             |   code added > (in green)
>>>>>>> BRANCH (378f8f commit2)     |
 (in red)                                                |

Here, I expect gerrit should have given a merge conflict.
But there was no merge conflict message.

Later the duplicate code was needed to be removed manually and then change was merged.
Here, I am trying to understand why gerrit did not give a merge conflict message when there was
a duplicate code.
This is actually quite important to since if merge does not
work as expected then how can we know what has been merged to the branch.

Can anyone please suggest how can I debug this situation or any pointer on how to find out what
could have caused this issue?

Thanks.
 

[David Pursehouse]

This is because the conflicts were not resolved before committing the
merge and pushing to Gerrit.

The "merge conflict" in Gerrit's UI is not related to the content of the
diff. It is shown when the commit cannot be merged into the repository
because of conflicts between the change and what is already in the
repository.

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[mani chandel]

On Tuesday, 8 July 2014 03:19:53 UTC+3, David Pursehouse wrote:

This is because the conflicts were not resolved before committing the
merge and pushing to Gerrit.

The "merge conflict" in Gerrit's UI is not related to the content of the
diff.  It is shown when the commit cannot be merged into the repository
because of conflicts between the change and what is already in the
repository.

 Ok, I understand. So is there any way I can know before pushing if there was a conflict?

Coz when I executed git merge <commit2> I did not get any message which says that there are conflicts.

[Saša Živkov]

On Tue, Jul 8, 2014 at 9:35 AM, mani chandel <mani.c...@gmail.com> wrote:

On Tuesday, 8 July 2014 03:19:53 UTC+3, David Pursehouse wrote:

This is because the conflicts were not resolved before committing the
merge and pushing to Gerrit.

The "merge conflict" in Gerrit's UI is not related to the content of the
diff.  It is shown when the commit cannot be merged into the repository
because of conflicts between the change and what is already in the
repository.

 Ok, I understand. So is there any way I can know before pushing if there was a conflict?

If there *was* a conflict during the merge of commit1 and commit2 Git would tell you and you would

know that before pushing.

 

Coz when I executed git merge <commit2> I did not get any message which says that there are conflicts.

This is what David already explained. What you see in Gerrit's UI is NOT a conflict

between the commit1 and commit2 but between the merge(commit1, commit2) and the tip

of the target branch.

 

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[Saša Živkov]

On Wed, Jul 16, 2014 at 5:06 PM, Saša Živkov <ziv...@gmail.com> wrote:

On Tue, Jul 8, 2014 at 9:35 AM, mani chandel <mani.c...@gmail.com> wrote:

On Tuesday, 8 July 2014 03:19:53 UTC+3, David Pursehouse wrote:

This is because the conflicts were not resolved before committing the
merge and pushing to Gerrit.

The "merge conflict" in Gerrit's UI is not related to the content of the
diff.  It is shown when the commit cannot be merged into the repository
because of conflicts between the change and what is already in the
repository.

 Ok, I understand. So is there any way I can know before pushing if there was a conflict?

If there *was* a conflict during the merge of commit1 and commit2 Git would tell you and you would

know that before pushing.

 

Coz when I executed git merge <commit2> I did not get any message which says that there are conflicts.

 

This is what David already explained. What you see in Gerrit's UI is NOT a conflict

between the commit1 and commit2 but between the merge(commit1, commit2) and the tip

of the target branch.

What I wrote above is nonsense :-(

So, you probably didn't resolve the conflicts before committing the merge... and the conflict markers

became part of the commit.

If this is not true and you really didn't have any conflicts on merge then I can only imagine that

in your local repository native Git auto resolved all the conflicts but then Gerrit couldn't auto-resolve

all of them and then shows the conflicts in the auto-merge version in the UI.

[Edwin Kempin]

2014-07-16 19:30 GMT+02:00 Saša Živkov <ziv...@gmail.com>:

On Wed, Jul 16, 2014 at 5:06 PM, Saša Živkov <ziv...@gmail.com> wrote:

On Tue, Jul 8, 2014 at 9:35 AM, mani chandel <mani.c...@gmail.com> wrote:

On Tuesday, 8 July 2014 03:19:53 UTC+3, David Pursehouse wrote:

This is because the conflicts were not resolved before committing the
merge and pushing to Gerrit.

The "merge conflict" in Gerrit's UI is not related to the content of the
diff.  It is shown when the commit cannot be merged into the repository
because of conflicts between the change and what is already in the
repository.

 Ok, I understand. So is there any way I can know before pushing if there was a conflict?

If there *was* a conflict during the merge of commit1 and commit2 Git would tell you and you would

know that before pushing.

 

Coz when I executed git merge <commit2> I did not get any message which says that there are conflicts.

 

This is what David already explained. What you see in Gerrit's UI is NOT a conflict

between the commit1 and commit2 but between the merge(commit1, commit2) and the tip

of the target branch.

What I wrote above is nonsense :-(

So, you probably didn't resolve the conflicts before committing the merge... and the conflict markers

became part of the commit.

If this is not true and you really didn't have any conflicts on merge then I can only imagine that

in your local repository native Git auto resolved all the conflicts but then Gerrit couldn't auto-resolve

all of them and then shows the conflicts in the auto-merge version in the UI.

Pay attention that for merge commits Gerrit shows you the version with the conflict markers as base so that you are able to review the conflict resolution (on the left side you see the conflicts and on the right side how they have been resolved).

[Saša Živkov]

This is correct. However,  Mani claims that no conflicts were reported on the merge in the local repository.

If this is true and the auto-merge version does show conflicts then I can only assume that the native

Git was able to resolve all the conflicts automatically and Gerrit (when creating the auto-merge) version

couldn't.

[mani chandel]

Hi Sasa,

I replicated this issue to test merge of these 2 particular commits many times

and every time I got the same result.

When I merged commit1 and commit2 

I did not get any error and got message that merge was successful (Here, I haven't pushed it to gerrit yet)

I checked the file where it was showing duplicate in gerrit diff view.

And I saw that file got all those duplicates in this step.

But there were no >>> >> <<< kind of marks showing conflicts in that file

nor were was there any conflict message when I executed git merge.

And then when I pushed to gerrit I got the result that I pasted in first post with >>><<< marks on left.

so then developer had to remove the duplicate manually from this file and upload a new patchset.

Every time I conducted this test of merging these 2 commits I got same result.

But this is weird and can cause problem if we do not get an indication of duplicates inserted

at any step :(

Thanks.

[Saša Živkov]

If this all was done without any mistakes on your side then it looks like a bug in the native Git.

Which Git version do you use locally?

 

But there were no >>> >> <<< kind of marks showing conflicts in that file

nor were was there any conflict message when I executed git merge.

And then when I pushed to gerrit I got the result that I pasted in first post with >>><<< marks on left.

so then developer had to remove the duplicate manually from this file and upload a new patchset.

Every time I conducted this test of merging these 2 commits I got same result.

The only way we could help would be to get access to these 2 commits and then reproduce the issue.

Could you provide it to us?

[mani chandel]

Hi Sasa,

I did some more testing with this issue.

Case 1:

1- Installed gerrit-2.8.5.

2- Pushed this merge commit to gerrit

Result: No merge conflict error on UI

Case 2:

1- Installed gerrit-2.9.

2- Pushed same merge commit to gerrit

Result: Merge Conflict error on gerrit UI (Cannot merge)

This is actually what is expected as there were duplicates introduced while creating merge commit.

Although at the time of merge git did not show any error.

But when upload to gerrit it is showing 'Cannot merge' so user can know that he needs to take an action here.

This is good. So I wanted to know if there is any change introduced in gerrit-2.9 which shows 'Cannot merge'

on UI for such changes.

Thanks.