[PATCH] Clarify documentation on commit message strip

[Fredrik Gustafsson <iveqy@iveqy.com>]

When using `-v` to add a unified diff to the commit message, this is
stripped and not a part of the commit message. This is not mentioned.

Add a note about this with the `-v` description as well as description
for the default `--cleanup` mode.

Signed-off-by: Fredrik Gustafsson <iveqy@iveqy.com>
---
 Documentation/git-commit.txt | 8 +++++---
 1 file changed, 5 insertions(+), 3 deletions(-)

diff --git a/Documentation/git-commit.txt b/Documentation/git-commit.txt
index 617e29b..e31d828 100644
--- a/Documentation/git-commit.txt
+++ b/Documentation/git-commit.txt
@@ -180,8 +180,9 @@ OPTIONS
 +
 --
 strip::
-	Strip leading and trailing empty lines, trailing whitespace, and
-	#commentary and collapse consecutive empty lines.
+	Strip leading and trailing empty lines, trailing whitespace,
+	#commentary, unified diff added with `-v` and collapse
+	consecutive empty lines.
 whitespace::
 	Same as `strip` except #commentary is not removed.
 verbatim::
@@ -283,7 +284,8 @@ configuration variable documented in linkgit:git-config[1].
 	Show unified diff between the HEAD commit and what
 	would be committed at the bottom of the commit message
 	template.  Note that this diff output doesn't have its
-	lines prefixed with '#'.
+	lines prefixed with '#'. This diff will not be a part
+	of the commit message.
 +
 If specified twice, show in addition the unified diff between
 what would be committed and the worktree files, i.e. the unstaged
-- 
2.1.4