#!/bin/sh

# An example hook script to update a checked-out tree on a git push.

#

# This hook is invoked by git-receive-pack(1) when it reacts to git

# push and updates reference(s) in its repository, and when the push

# tries to update the branch that is currently checked out and the

# receive.denyCurrentBranch configuration variable is set to

# updateInstead.

#

# By default, such a push is refused if the working tree and the index

# of the remote repository has any difference from the currently

# checked out commit; when both the working tree and the index match

# the current commit, they are updated to match the newly pushed tip

# of the branch. This hook is to be used to override the default

# behaviour; however the code below reimplements the default behaviour

# as a starting point for convenient modification.

#

# The hook receives the commit with which the tip of the current

# branch is going to be updated:

commit=$1

# It can exit with a non-zero status to refuse the push (when it does

# so, it must not modify the index or the working tree).

die () {

	echo >&2 "$*"

	exit 1

}

# Or it can make any necessary changes to the working tree and to the

# index to bring them to the desired state when the tip of the current

# branch is updated to the new commit, and exit with a zero status.

#

# For example, the hook can simply run git read-tree -u -m HEAD "$1"

# in order to emulate git fetch that is run in the reverse direction

# with git push, as the two-tree form of git read-tree -u -m is

# essentially the same as git switch or git checkout that switches

# branches while keeping the local changes in the working tree that do

# not interfere with the difference between the branches.

# The below is a more-or-less exact translation to shell of the C code

# for the default behaviour for git's push-to-checkout hook defined in

# the push_to_deploy() function in builtin/receive-pack.c.

#

# Note that the hook will be executed from the repository directory,

# not from the working tree, so if you want to perform operations on

# the working tree, you will have to adapt your code accordingly, e.g.

# by adding "cd .." or using relative paths.

if ! git update-index -q --ignore-submodules --refresh

then

	die "Up-to-date check failed"

fi

if ! git diff-files --quiet --ignore-submodules --

then

	die "Working directory has unstaged changes"

fi

# This is a rough translation of:

#

#   head_has_history() ? "HEAD" : EMPTY_TREE_SHA1_HEX

if git cat-file -e HEAD 2>/dev/null

then

	head=HEAD

else

	head=$(git hash-object -t tree --stdin </dev/null)

fi

if ! git diff-index --quiet --cached --ignore-submodules $head --

then

	die "Working directory has staged changes"

fi

if ! git read-tree -u -m "$commit"

then

	die "Could not update working tree to new HEAD"

fi