range-diff doc: add a section about output stability

diff --git a/Documentation/git-format-patch.txt b/Documentation/git-format-patch.txt
index 9b2e17215999cc56553ed3234e6084bc7cc8a580..aba4c5febeb7ef4248d50a638d0a8bd58f7d553b 100644 (file)
--- a/Documentation/git-format-patch.txt
+++ b/Documentation/git-format-patch.txt
@@ -241,7 +241,8 @@ feeding the result to `git send-email`.
 
 --range-diff=<previous>::
        As a reviewer aid, insert a range-diff (see linkgit:git-range-diff[1])
-       into the cover letter showing the differences between the previous
+       into the cover letter, or as commentary of the lone patch of a
+       1-patch series, showing the differences between the previous
        version of the patch series and the series currently being formatted.
        `previous` can be a single revision naming the tip of the previous
        series if it shares a common base with the series being formatted (for