test-command-template: add a short description of a temporary snippet

This snippet was introduced by c1cb6523e968. Its purpose seems a bit
obscure without historical context.

tests/test-command-template.t

@@ -94,12 +94,15 b' Template should precede style option'
   $ hg log -l1 --style default -T '{rev}\n'
   8
 
-Default style is like normal output:
+Add a commit with empty description, to ensure that the templates
+following below omit it properly.
 
   $ echo c >> c
   $ hg add c
   $ hg commit -qm ' '
 
+Default style is like normal output.
+
   $ hg log > log.out
   $ hg log --style default > style.out
   $ cmp log.out style.out || diff -u log.out style.out
@@ -139,6 +142,9 b' Default style should also preserve color'
 
   $ mv $HGRCPATH-bak $HGRCPATH
 
+Remove commit with empty commit message, so as to not pollute further
+tests.
+
   $ hg --config extensions.strip= strip -q .
 
 Revision with no copies (used to print a traceback):