Re: Emacs git repo mangled

[Gregory Heytings <gregory@heytings.org>]

>> By definition, the bad commit cannot be inside the merged Eglot tree, 
>> because that tree contains only Eglot, not Emacs.  The bad commit could 
>> be the merge commit, but that one is not excluded during the bisection 
>> if you mark the last commit before the merge as "good".
>
> That's the eglot case. I was speaking about a merge in general.
>

Yes, and it's because of merges in general that using --first-parent is 
not a good idea.

>> Perhaps we could maintain a list of such merges somewhere, with the 
>> commit SHA of the last commit before each merge.  Or perhaps even a 
>> commented script, that would do a "git bisect good ..." for each such 
>> commit.
>
> Don't know, I let it to the git aficionados.
>

Eglot's merge (0186faf2a1) is the first case in Emacs' history in which 
another root commit (1e5b753bf4) was added to the repository.  So at the 
moment there is only one such command to type when starting a bisection: 
git bisect good 806734c1b1.

Eli, what do you think of adding an admin/git-bisect script to do that? 
In the future, if other similar merges are done, it would suffice to add 
another such line in that file.