How to find the base version cf-bot is using?

Hello. I found that the CF-bot is complaining on one of my patch.

http://cfbot.cputube.org/patch_18_931.log

> === applying patch ./v4-0001-Remove-entries-that-haven-t-been-used-for-a-certain-.patch
...
> |Date: Tue, 26 Dec 2017 17:43:09 +0900
...
> Patching file src/backend/utils/cache/plancache.c using Plan A...
> Hunk #1 failed at 63.
> Hunk #2 failed at 88.
> Hunk #3 failed at 113.
> Hunk #4 succeeded at 296 with fuzz 2 (offset 79 lines).
> Hunk #5 succeeded at 388 with fuzz 1 (offset -46 lines).
> Hunk #6 failed at 457.
> Hunk #7 failed at 484.
> Hunk #8 failed at 498.
> Hunk #9 failed at 542.
> Hunk #10 succeeded at 1321 with fuzz 2 (offset 115 lines).
> Hunk #11 failed at 1340.
> Hunk #12 failed at 1357.
> Hunk #13 succeeded at 1983 with fuzz 1 (offset 48 lines).
> 9 out of 13 hunks failed--saving rejects to src/backend/utils/cache/plancache.c.rej

On the other hand the same patch cleanly applies on the master
HEAD with no offsets.

> $ patch -p1 < ~/work/patches/v4-0001-Remove-entries-that-haven-t-been-used-for-a-certain-.patch
> patching file doc/src/sgml/config.sgml
> patching file src/backend/access/transam/xact.c
> patching file src/backend/utils/cache/catcache.c
> patching file src/backend/utils/cache/plancache.c
> patching file src/backend/utils/misc/guc.c
> patching file src/backend/utils/misc/postgresql.conf.sample
> patching file src/include/utils/catcache.h
> patching file src/include/utils/plancache.h
> {work}[pg(at)master]$ git status
> On branch master
> Your branch is up to date with 'origin/master'.
> ...
> $ git log -1
> commit a33969ee918aafdb9086be27d7d63b129b4bfc44 (HEAD -> master, origin/master, origin/HEAD)
> Author: Peter Eisentraut <peter_e(at)gmx(dot)net>
> Date: Sun Jul 1 15:10:08 2018 +0200

How can I find the base version the CF-bot used at the time?

regards.

--
Kyotaro Horiguchi
NTT Open Source Software Center