misc: Clarify commit message guidelines

This change in wording aims towards a more welcoming first review
atmosphere for new contributors. I was recently reading through a
chain of very-high-quality commits from a first-time contributor,
and the only problem was the conjugation of the commit message.
This is a totally minor issue but when I am scanning through a list
of a thousand commit messages in imperative mood and there is one
standing out in past indicative, it throws off my concentration.
Now I am left with a dilemma on my hands: I don't want the risk of
mistaken impression of undue nitpicking over undocumented style
preference, in a good commit from a new contributor. The present
change borrows additional explanatory language from Eclipse's Commit
Guidelines, to avoid this kind of tensions in the future.

Change-Id: If6aa8341871304ee7ff88a014048e4104aa9dcb5
Reviewed-on: https://gem5-review.googlesource.com/c/public/gem5/+/60129
Maintainer: Jason Lowe-Power <power.jg@gmail.com>
Tested-by: kokoro <noreply+kokoro@google.com>
Reviewed-by: Jason Lowe-Power <power.jg@gmail.com>
Reviewed-by: Bobby Bruce <bbruce@ucdavis.edu>
1 file changed