Which git hash to supply on Fixes: line

[Mark Geisert]

Hi folks,
I want to submit a patch that fixes 'profiler'.  The Fixes: line of the 
patch commentary should reference the original addition of profiler to the 
Cygwin source tree.

Using the gitweb interface, the commit display of profiler.cc shows:
author	  Mark Geisert <mark@maxrnd.com>  2021-07-15 21:49:55 -0700
committer Jon Turney <jon.turney@...>     2021-07-19 13:28:37 +0100
commit	9bd6c0b2b1081ae72d8273038309887fb27f6126 (patch)
tree	360d7d3cc748683eb9e63729a7e52a62012730e4 /winsup/utils/profiler.cc
parent	Cygwin: cfsetspeed: allow speed to be a numerical baud rate (diff)

Do I use the last 13 nibbles of the "commit" hash or the "tree" hash?

First time I've seen both; on previous patches I've supplied a hash but 
I'm not sure which one of these they were because I was relying on some 
other method to find them.
Thanks,

..mark