Add sample pre-push hook script

Create a sample of a script for a pre-push hook.  The main purpose is to
illustrate how a script may parse the information which is supplied to
such a hook.  The script may also be useful to some people as-is for
avoiding to push commits which are marked as a work in progress.

Signed-off-by: Aaron Schrab <aaron@schrab.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

diff --git a/templates/hooks--pre-push.sample b/templates/hooks--pre-push.sample
new file mode 100644 (file)
index 0000000..15ab6d8
--- /dev/null
+++ b/templates/hooks--pre-push.sample
@@ -0,0 +1,53 @@
+#!/bin/sh
+
+# An example hook script to verify what is about to be pushed.  Called by "git
+# push" after it has checked the remote status, but before anything has been
+# pushed.  If this script exits with a non-zero status nothing will be pushed.
+#
+# This hook is called with the following parameters:
+#
+# $1 -- Name of the remote to which the push is being done
+# $2 -- URL to which the push is being done
+#
+# If pushing without using a named remote those arguments will be equal.
+#
+# Information about the commits which are being pushed is supplied as lines to
+# the standard input in the form:
+#
+#   <local ref> <local sha1> <remote ref> <remote sha1>
+#
+# This sample shows how to prevent push of commits where the log message starts
+# with "WIP" (work in progress).
+
+remote="$1"
+url="$2"
+
+z40=0000000000000000000000000000000000000000
+
+IFS=' '
+while read local_ref local_sha remote_ref remote_sha
+do
+       if [ "$local_sha" = $z40 ]
+       then
+               # Handle delete
+       else
+               if [ "$remote_sha" = $z40 ]
+               then
+                       # New branch, examine all commits
+                       range="$local_sha"
+               else
+                       # Update to existing branch, examine new commits
+                       range="$remote_sha..$local_sha"
+               fi
+
+               # Check for WIP commit
+               commit=`git rev-list -n 1 --grep '^WIP' "$range"`
+               if [ -n "$commit" ]
+               then
+                       echo "Found WIP commit in $local_ref, not pushing"
+                       exit 1
+               fi
+       fi
+done
+
+exit 0