post-checkout hook, tests, and docs

Updated post-checkout hook to take a flag specifying whether the checkout is
a branch checkout or a file checkout (from the index).

Signed-off-by: Josh England <jjengla@sandia.gov>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

1 files changed, 14 insertions, 0 deletions

diff --git a/Documentation/hooks.txt b/Documentation/hooks.txt
index 58b9547..f110162 100644
--- a/Documentation/hooks.txt
+++ b/Documentation/hooks.txt
@@ -87,6 +87,20 @@ parameter, and is invoked after a commit is made.
 This hook is meant primarily for notification, and cannot affect
 the outcome of `git-commit`.
 
+post-checkout
+-----------
+
+This hook is invoked when a `git-checkout` is run after having updated the
+worktree.  The hook is given three parameters: the ref of the previous HEAD,
+the ref of the new HEAD (which may or may not have changed), and a flag
+indicating whether the checkout was a branch checkout (changing branches,
+flag=1) or a file checkout (retrieving a file from the index, flag=0).
+This hook cannot affect the outcome of `git-checkout`.
+
+This hook can be used to perform repository validity checks, auto-display
+differences from the previous HEAD if different, or set working dir metadata
+properties.
+
 post-merge
 -----------