The Einstein minus convention, lost In his milestone paper on general relativity, Einstein not only introduces the Einstein summation convention, but also (formula (45) in [1]) abbreviates a minus at the Christoffel symbols away by introducing the Gamma notation for the connection coefficients of his variant of the covariant derivative, constructed on cotangent space first from given geodesics.
In later standard literature the minus is gone. (E.g. Schrödinger p.66 [3])
Why, and who dropped it?

Addendum/scholium:
Thanks for linking from a related question on
https://hsm.stackexchange.com/questions/7974/notation-for-christoffel-symbols !
The physical relevance of that sign might explain why it is gone, and I first thought about not asking on mathoverflow. But Einstein's introduction of the covariant derivative strikes me as masterful abstract differential geometry (of his time). Plus, it can be simplified and abstracted to general symmetric connections with given geodesics without Christoffel symbol stuff (if I'm not mistaken).
I have not yet found it in other literature.
(Already the standard geodesic equation with Christoffel symbols looks like an ugly case of superfluous zero to me. Like Einstein I prefer an own side for the 2nd derivative.)

[1] A.Einstein: Die Grundlage der allgemeinen Relativitätstheorie (1916) p.802
https://web.archive.org/web/20060830030952/http://www.alberteinstein.info/gallery/pdf/CP6Doc30_pp284-339.pdf
[2] Manuscript of [1], translation and more:
H.Gutfreund, J.Renn: The Road to Relativity (2015) p.92 (German manuscript facsimile) p.209 (English translation).
https://press.princeton.edu/books/hardcover/9780691162539/the-road-to-relativity
[3] E.Schrödinger: Space-Time Structure (1950/4)
https://www.cambridge.org/core/books/spacetime-structure/554B50728DF38139E42E60BBED654D85
 A: • Why Einstein introduced a minus sign in the definition of the second Christoffel symbol $\Gamma^\sigma_{\mu\nu}$:
He writes just below equation (45) in Ref. 1:

So he wanted to identify the $\Gamma^\sigma_{\mu\nu}$ with the components of the gravitational field, and for that identification the minus sign is needed.
• Why was the minus sign dropped?
It was understood that the identification of the Christoffel symbol with the gravitational field is mistaken: you can have a nonzero $\Gamma^\sigma_{\mu\nu}$ and zero gravitational field, all you have to do is to introduce curved coordinate systems in flat space. And conversely, the Christoffel symbol can vanish along a geodesic even if the gravitational field is nonzero.

Addendum: It seems Einstein was also not quite consistent with respect to the minus sign; in a 1914 paper he defined the $\Gamma$ without the minus sign:

In an interesting discussion on HSM it is suggested Einstein chose the symbol $\Gamma$ to refer to the first letter of "Gravitation".
A: Since the question has now narrowed down to "who lost the minus sign" in the Christoffel symbol, let me start a new thread: The OP asks for a reputable source, later than Einstein's 1916 paper, in which the minus sign is abandoned. I propose that it was Einstein himself who dropped it. Below I copy from his 1921 lectures at Princeton University, page 46:

