I'm not sure what does "those errors" refers to.

AFAICS, emacs-repository-{brach|version}-git use `with-demoted-errors' to catch git

errors and make them into messages, but these messages do not show in the output

when compiling or bootstrapping:

Loading tooltip...
Loading international/iso-transl...
Loading leim/leim-list.el (source)...
Loading emacs-lisp/rmc...
Waiting for git...
Waiting for git...
Finding pointers to doc strings...
Finding pointers to doc strings...done
Growing hash table to: 120000
Pure-hashed: 18444 strings, 5733 vectors, 51813 conses, 5185 bytecodes, 341 others
Dumping under the name emacs.pdmp
Dumping fingerprint: c7027ccc5a785a5e006e026f442c029d10eb642c13dd475b88c5946e2e0c349e
Dump complete

There's only "Waiting for git" (in the above log, both git calls failed because of

the same "admins vs current user" issue than my original report).