Wording improvements

Describe how to collapse multiple MFCs better. Use consistent punctuation. fix
some typos.

Submitted by: Pau Amma

documentation/content/en/articles/committers-guide/_index.adoc

@@ -720,7 +720,8 @@ use `git pull --rebase` and try to push again.
 % for h in $HASH_LIST; do git cherry-pick -x $h; done
 % git rebase -i stable/X
 # mark each of the commits after the first as 'squash'
-# edit the commit message to be sane, if necessary
+# Update the commit message to reflect all elements of commit, if necessary.
+# Be sure to retain the "cherry picked from" lines.
 % git push freebsd HEAD:stable/X
 ....
 
@@ -1338,7 +1339,7 @@ At this point, you should have a pristine copy of glorbnitz ready to commit.
 ....
 As above, I used `-m` for simplicity, but you should likely create a commit message that explains what a Glorb is and why you'd use a Nitz to get it.
 Not everybody will know.
-But for your actual commmit, you should follow the <<commit-log-message,commit log message>> section instead of emulate the brief style here.
+But for your actual commit, you should follow the <<commit-log-message,commit log message>> section instead of emulating the brief style used here.
 
 ==== Now import it into our repository
 Now you need to import the branch into our repository.
@@ -1369,7 +1370,7 @@ By 'good' we mean:
 . All the right files are present
 . None of the wrong files are present
 . The vendor branch points at something sensible
-. The tag looks good, and is annotated.
+. The tag looks good, and is annotated
 . The commit message for the tag has a quick summary of what's new since the last tag
 
 ==== Time to finally merge it into the base tree