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Cannot Open Compare Editor - This is a merge commit with more than one ancestor [message #1828789]

Thu, 18 June 2020 14:42

Albert Kao

Messages: 11
Registered: April 2016

Junior Member

This error screen popup when comparing with previous version.
error screen title : Cannot Open Compare Editor
error screen message : This is a merge commit with more than one ancestor

How to solve this issue?

Thanks.

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Re: Cannot Open Compare Editor - This is a merge commit with more than one ancestor [message #1828814 is a reply to message #1828789]

Fri, 19 June 2020 07:04

Thomas Wolf

Messages: 576
Registered: August 2016

Senior Member

More details needed.

Which EGit version?
How exactly are you trying to open the compare editor? (Which menu, where (in the package explorer? in an editor? in the history view?), what's the current selection?)

Current HEAD in your git repository seems to be at a merge commit.

In general, EGit cannot show the compare editor in this case since it doesn't know against which parent commit you want to compare. In some cases we might add something to let the user choose the parent commit to compare against, which is why I'd like to know what exactly you're doing.

A possible work-around with EGit 5.8.0 might be to select the merge commit and the parent commit wanted in the history view, then use "Show Unified Diff" from the context menu. To see a side-by-side diff of one file, use the link available on a hunk header (on the numbers in the @@ lines).

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Re: Cannot Open Compare Editor - This is a merge commit with more than one ancestor [message #1828834 is a reply to message #1828814]

Fri, 19 June 2020 14:20

Albert Kao

Messages: 11
Registered: April 2016

Junior Member

version : m2e 1.9.1.20180912-1601 Eclipse Java EE IDE for Web Developers 2018-09 (4.9.0)
Steps to reproduce this error:
History View
Select any one file in a specific commit which is a merge commit with more than one ancestor.
Right click.
"Compare with Previous Version" option popup.
Click the "Compare with Previous Version" option.
This error screen popup when comparing with previous version.
error screen title : Cannot Open Compare Editor
error screen message : This is a merge commit with more than one ancestor

[Updated on: Fri, 19 June 2020 14:26]

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Re: Cannot Open Compare Editor - This is a merge commit with more than one ancestor [message #1828838 is a reply to message #1828834]

Fri, 19 June 2020 15:55

Thomas Wolf

Messages: 576
Registered: August 2016

Senior Member

We might indeed ask the user at that point which parent he wants to compare against. Please open an enhancement request at https://bugs.eclipse.org/bugs/enter_bug.cgi?product=EGit .

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