/usr/share/gitit/data/post-update is in libghc-gitit-data 0.12.1-1.
This file is owned by root:root, with mode 0o755.
The actual contents of the file can be viewed below.
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85  | #!/bin/sh
#
# This hook does two things:
#
#  1. update the "info" files that allow the list of references to be
#     queries over dumb transports such as http
#
#  2. if this repository looks like it is a non-bare repository, and
#     the checked-out branch is pushed to, then update the working copy.
#     This makes "push" function somewhat similarly to darcs and bzr.
#
# To enable this hook, make this file executable by "chmod +x post-update".
git update-server-info
is_bare=$(git config --get --bool core.bare)
if [ -z "$is_bare" ]
then
	# for compatibility's sake, guess
	git_dir_full=$(cd $GIT_DIR; pwd)
	case $git_dir_full in */.git) is_bare=false;; *) is_bare=true;; esac
fi
update_wc() {
	ref=$1
	echo "Push to checked out branch $ref" >&2
	if [ ! -f $GIT_DIR/logs/HEAD ]
	then
		echo "E:push to non-bare repository requires a HEAD reflog" >&2
		exit 1
	fi
	if (cd $GIT_WORK_TREE; git diff-files -q --exit-code >/dev/null)
	then
		wc_dirty=0
	else
		echo "W:unstaged changes found in working copy" >&2
		wc_dirty=1
		desc="working copy"
	fi
	if git diff-index --cached HEAD@{1} >/dev/null
	then
		index_dirty=0
	else
		echo "W:uncommitted, staged changes found" >&2
		index_dirty=1
		if [ -n "$desc" ]
		then
			desc="$desc and index"
		else
			desc="index"
		fi
	fi
	if [ "$wc_dirty" -ne 0 -o "$index_dirty" -ne 0 ]
	then
		new=$(git rev-parse HEAD)
		echo "W:stashing dirty $desc - see git-stash(1)" >&2
		( trap 'echo trapped $$; git symbolic-ref HEAD "'"$ref"'"' 2 3 13 15 ERR EXIT
		git update-ref --no-deref HEAD HEAD@{1}
		cd $GIT_WORK_TREE
		git stash save "dirty $desc before update to $new";
		git symbolic-ref HEAD "$ref"
		)
	fi
	# eye candy - show the WC updates :)
	echo "Updating working copy" >&2
	(cd $GIT_WORK_TREE
	git diff-index -R --name-status HEAD >&2
	git reset --hard HEAD)
}
if [ "$is_bare" = "false" ]
then
	active_branch=`git symbolic-ref HEAD`
	export GIT_DIR=$(cd $GIT_DIR; pwd)
	GIT_WORK_TREE=${GIT_WORK_TREE-..}
	for ref
	do
		if [ "$ref" = "$active_branch" ]
		then
			update_wc $ref
		fi
	done
fi
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