If the user has opted to not share their email address on github, then nothing on the github web UI (or github Rest API) will expose it to you.
The best (and possibly only) option you have is to clone their repo (tip: do a shallow clone) and look at the branch and commit sha details referenced in the PR ...
[tmp]$ git clone -b master --single-branch git@xxxxxxxxxx:fipro78/eclipse-collections.git --depth=3
Cloning into 'eclipse-collections'...
remote: Enumerating objects: 3910, done.
remote: Counting objects: 100% (3910/3910), done.
remote: Compressing objects: 100% (2111/2111), done.
remote: Total 3910 (delta 2571), reused 2189 (delta 1614), pack-reused 0
Receiving objects: 100% (3910/3910), 3.45 MiB | 11.47 MiB/s, done.
Resolving deltas: 100% (2571/2571), done.
[tmp]$ cd eclipse-collections/
[eclipse-collections][master]$ git log -1 --pretty=fuller 45c2452cb69f28445ed0e146b41549053454e8dd
commit 45c2452cb69f28445ed0e146b41549053454e8dd (HEAD -> master, origin/master, origin/HEAD)
Author: Dirk Fauth <dirk.fauth@***.com>
AuthorDate: Wed Feb 3 09:27:55 2021 +0100
Commit: Dirk Fauth <dirk.fauth@***.com>
CommitDate: Thu Feb 4 06:55:50 2021 +0100
Use Maven Locations for p2 update site build
Signed-off-by: Dirk Fauth <dirk.fauth@***.com>
Note: I've edited his email address (to "@***.com") to satisfy Eclipse Foundation rules on exposing email addresses.
If you run the commands yourself, you'll see the email address clearly.
- Joakim