git-rev-list.txt: tweak wording in set operations

Tweak a sentence to make it a little more readable.

Signed-off-by: Philippe Blain <levraiphilippeblain@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

Documentation/git-rev-list.txt

@@ -19,12 +19,12 @@ given commit(s), but exclude commits that are reachable from the one(s)
 given with a '{caret}' in front of them.  The output is given in reverse
 chronological order by default.
 
-You can think of this as a set operation.  Commits given on the command
+You can think of this as a set operation. Commits reachable from any of
-line form a set of commits that are reachable from any of them, and then
+the commits given on the command line form a set, and then commits reachable
-commits reachable from any of the ones given with '{caret}' in front are
+from any of the ones given with '{caret}' in front are subtracted from that
-subtracted from that set.  The remaining commits are what comes out in the
+set.  The remaining commits are what comes out in the command's output.
-command's output.  Various other options and paths parameters can be used
+Various other options and paths parameters can be used to further limit the
-to further limit the result.
+result.
 
 Thus, the following command: