[PATCH] Documentation/git-patch-id: give working code example

[Michael J Gruber <git@drmicha.warpmail.net>]

As it stands, the documentation gives the impression that

git diff-tree <treeish> | git patch-id

would be a working invocation of git patch-id, leaving the novice user
in the dark.

Make it explicit that 'git diff-tree -p' would be the command to use.

Signed-off-by: Michael J Gruber <git@drmicha.warpmail.net>
---
 Documentation/git-patch-id.txt | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/Documentation/git-patch-id.txt b/Documentation/git-patch-id.txt
index cf71fba..67f8e28 100644
--- a/Documentation/git-patch-id.txt
+++ b/Documentation/git-patch-id.txt
@@ -21,7 +21,7 @@ have the same "patch ID" are almost guaranteed to be the same thing.
 
 IOW, you can use this thing to look for likely duplicate commits.
 
-When dealing with 'git diff-tree' output, it takes advantage of
+When dealing with 'git diff-tree -p' output, it takes advantage of
 the fact that the patch is prefixed with the object name of the
 commit, and outputs two 40-byte hexadecimal strings.  The first
 string is the patch ID, and the second string is the commit ID.
-- 
2.10.0.rc0.268.ge3ba28a