Re: How to debug a "git merge"?

From: Derrick Stolee <stolee@gmail.com>
Date: Mar 14, 2018, 17:02 UTC
Message-ID: <ddde09e9-0524-23f8-3585-ac00c2ec7f45@gmail.com>
In-Reply-To: <7895279B-9FB6-471B-A8BA-53315B265A51@gmail.com>

On 3/14/2018 12:56 PM, Lars Schneider wrote:

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> Hi,
>
> I am investigating a Git merge (a86dd40fe) in which an older version of
> a file won over the newer version. I try to understand why this is the
> case. I can reproduce the merge with the following commands:
> $ git checkout -b test a02fa3303
> $ GIT_MERGE_VERBOSITY=5 git merge --verbose c1b82995c
>
> The merge actually generates a merge conflict but not for my
> problematic file. The common ancestor of the two parents (merge base)
> is b91161554.
>
> The merge graph is not pretty (the committers don't have a clean
> branching scheme) but I cannot spot a problem between the merge commit
> and the common ancestor:
> $ git log --graph --oneline a86dd40fe

Have you tried `git log --graph --oneline --simplify-merges -- path` to see what changes and merges involved the file? I find that view to be very helpful (while the default history simplification can hide things). In particular, if there was a change that was reverted in one side and not another, we could find out.

You could also use the "A...B" to check your two commits for merging, and maybe add "--boundary".

Show 8 quoted lines

>
> Can you give me a hint how to debug this merge further? How can I
> understand why Git picked a certain version of a file in a merge?
>
> I am using Git 2.16.2 on Linux.
>
> Thanks,
> Lars