[PATCH] Clarify pre-push hook documentation

[David Cowden <dcow90@gmail.com>]

The documentation as-is does not mention that the pre-push hook is
executed even when there is nothing to push.  This can lead a new
reader to beilieve there will always be lines fed to the script's
standerd input and cause minor confusion as to what is happening
when there are no lines provided to the pre-push script.

Signed-off-by: David Cowden <dcow90@gmail.com>
---

Notes:
    c.f. http://stackoverflow.com/questions/22585091/git-hooks-pre-push-script-does-not-receive-input-via-stdin

 Documentation/githooks.txt | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/Documentation/githooks.txt b/Documentation/githooks.txt
index d954bf6..a28f6f7 100644
--- a/Documentation/githooks.txt
+++ b/Documentation/githooks.txt
@@ -203,6 +203,10 @@ SHA-1>` will be 40 `0`.  If the local commit was specified by something other
 than a name which could be expanded (such as `HEAD~`, or a SHA-1) it will be
 supplied as it was originally given.
 
+The hook is executed regardless of whether there are changes to push or not.
+In the event that there are no changes, no data will be provided on the
+script's standard input.
+
 If this hook exits with a non-zero status, 'git push' will abort without
 pushing anything.  Information about why the push is rejected may be sent
 to the user by writing to standard error.
-- 
1.9.1