1#!/bin/sh
2
3# An example hook script to update a checked-out tree on a git push.
4#
5# This hook is invoked by git-receive-pack(1) when it reacts to git
6# push and updates reference(s) in its repository, and when the push
7# tries to update the branch that is currently checked out and the
8# receive.denyCurrentBranch configuration variable is set to
9# updateInstead.
10#
11# By default, such a push is refused if the working tree and the index
12# of the remote repository has any difference from the currently
13# checked out commit; when both the working tree and the index match
14# the current commit, they are updated to match the newly pushed tip
15# of the branch. This hook is to be used to override the default
16# behaviour; however the code below reimplements the default behaviour
17# as a starting point for convenient modification.
18#
19# The hook receives the commit with which the tip of the current
20# branch is going to be updated:
21commit=$1
22
23# It can exit with a non-zero status to refuse the push (when it does
24# so, it must not modify the index or the working tree).
25die () {
26	echo >&2 "$*"
27	exit 1
28}
29
30# Or it can make any necessary changes to the working tree and to the
31# index to bring them to the desired state when the tip of the current
32# branch is updated to the new commit, and exit with a zero status.
33#
34# For example, the hook can simply run git read-tree -u -m HEAD "$1"
35# in order to emulate git fetch that is run in the reverse direction
36# with git push, as the two-tree form of git read-tree -u -m is
37# essentially the same as git switch or git checkout that switches
38# branches while keeping the local changes in the working tree that do
39# not interfere with the difference between the branches.
40
41# The below is a more-or-less exact translation to shell of the C code
42# for the default behaviour for git's push-to-checkout hook defined in
43# the push_to_deploy() function in builtin/receive-pack.c.
44#
45# Note that the hook will be executed from the repository directory,
46# not from the working tree, so if you want to perform operations on
47# the working tree, you will have to adapt your code accordingly, e.g.
48# by adding "cd .." or using relative paths.
49
50if ! git update-index -q --ignore-submodules --refresh
51then
52	die "Up-to-date check failed"
53fi
54
55if ! git diff-files --quiet --ignore-submodules --
56then
57	die "Working directory has unstaged changes"
58fi
59
60# This is a rough translation of:
61#
62#   head_has_history() ? "HEAD" : EMPTY_TREE_SHA1_HEX
63if git cat-file -e HEAD 2>/dev/null
64then
65	head=HEAD
66else
67	head=$(git hash-object -t tree --stdin </dev/null)
68fi
69
70if ! git diff-index --quiet --cached --ignore-submodules $head --
71then
72	die "Working directory has staged changes"
73fi
74
75if ! git read-tree -u -m "$commit"
76then
77	die "Could not update working tree to new HEAD"
78fi
79