#!/bin/sh

setglobal OPTIONS_KEEPDASHDASH = 't'
setglobal OPTIONS_SPEC = '"\
git-checkout [options] [<branch>] [<paths>...]
--
b=          create a new branch started at <branch>
l           create the new branch's reflog
track       arrange that the new branch tracks the remote branch
f           proceed even if the index or working tree is not HEAD
m           merge local modifications into the new branch
q,quiet     be quiet
'"
setglobal SUBDIRECTORY_OK = 'Sometimes'
source git-sh-setup
require_work_tree

setglobal old_name = 'HEAD'
setglobal old = $[git rev-parse --verify $old_name !2 >/dev/null]
setglobal oldbranch = $[git symbolic-ref $old_name !2 >/dev/null]
setglobal new = ''
setglobal new_name = ''
setglobal force = ''
setglobal branch = ''
setglobal track = ''
setglobal newbranch = ''
setglobal newbranch_log = ''
setglobal merge = ''
setglobal quiet = ''
setglobal v = '-v'
setglobal LF = ''
''

while test $Argc != 0 {
	match $1 {
	with -b
		shift
		setglobal newbranch = $1
		test -z $newbranch &&
			die "git checkout: -b needs a branch name"
		git show-ref --verify --quiet -- "refs/heads/$newbranch" &&
			die "git checkout: branch $newbranch already exists"
		git check-ref-format "heads/$newbranch" ||
			die "git checkout: we do not like '$newbranch' as a branch name."
		
	with -l
		setglobal newbranch_log = '-l'
		
	with --track|--no-track
		setglobal track = $1
		
	with -f
		setglobal force = '1'
		
	with -m
		setglobal merge = '1'
		
	with -q|--quiet
		setglobal quiet = '1'
		setglobal v = ''
		
	with --
		shift
		break
		
	with *
		usage
		
	}
	shift
}

setglobal arg = $1
setglobal rev = $[git rev-parse --verify $arg !2 >/dev/null]
if setglobal rev = $[git rev-parse --verify "$rev^0" !2 >/dev/null]
{
	test -z $rev && die "unknown flag $arg"
	setglobal new_name = $arg
	if git show-ref --verify --quiet -- "refs/heads/$arg"
	{
		setglobal rev = $[git rev-parse --verify "refs/heads/$arg^0]
		setglobal branch = $arg
	}
	setglobal new = $rev
	shift
} elif setglobal rev = $[git rev-parse --verify "$rev^{tree}" !2 >/dev/null]
{
	# checking out selected paths from a tree-ish.
	setglobal new = $rev
	setglobal new_name = ""$rev^{tree}""
	shift
}
test $1 = "--" && shift

match "$newbranch,$track" {
with ,--*
	die "git checkout: --track and --no-track require -b"
}

match "$force$merge" {
with 11
	die "git checkout: -f and -m are incompatible"
}

# The behaviour of the command with and without explicit path
# parameters is quite different.
#
# Without paths, we are checking out everything in the work tree,
# possibly switching branches.  This is the traditional behaviour.
#
# With paths, we are _never_ switching branch, but checking out
# the named paths from either index (when no rev is given),
# or the named tree-ish (when rev is given).

if test "$Argc" -ge 1
{
	setglobal hint = ''
	if test "$Argc" -eq 1
	{
		setglobal hint = ""
Did you intend to checkout '$ifsjoin(Argv)' which can not be resolved as commit?""
	}
	if test '' != "$newbranch$force$merge"
	{
		die "git checkout: updating paths is incompatible with switching branches/forcing$hint"
	}
	if test '' != $new
	{
		# from a specific tree-ish; note that this is for
		# rescuing paths and is never meant to remove what
		# is not in the named tree-ish.
		git ls-tree --full-name -r $new @Argv |
		git update-index --index-info || exit $?
	}

	# Make sure the request is about existing paths.
	git ls-files --full-name --error-unmatch -- @Argv >/dev/null || exit
	git ls-files --full-name -- @Argv |
		shell {cd_to_toplevel && git checkout-index -f -u --stdin}

	# Run a post-checkout hook -- the HEAD does not change so the
	# current HEAD is passed in for both args
	if test -x "$GIT_DIR"/hooks/post-checkout {
	    "$GIT_DIR"/hooks/post-checkout $old $old 0
	}

	exit $?
} else {
	# Make sure we did not fall back on $arg^{tree} codepath
	# since we are not checking out from an arbitrary tree-ish,
	# but switching branches.
	if test '' != $new
	{
		git rev-parse --verify "$new^{commit}" >/dev/null !2 > !1 ||
		die "Cannot switch branch to a non-commit."
	}
}

# We are switching branches and checking out trees, so
# we *NEED* to be at the toplevel.
cd_to_toplevel

test -z $new && setglobal new = $old && setglobal new_name = $old_name

# If we don't have an existing branch that we're switching to,
# and we don't have a new branch name for the target we
# are switching to, then we are detaching our HEAD from any
# branch.  However, if "git checkout HEAD" detaches the HEAD
# from the current branch, even though that may be logically
# correct, it feels somewhat funny.  More importantly, we do not
# want "git checkout" or "git checkout -f" to detach HEAD.

setglobal detached = ''
setglobal detach_warn = ''

proc describe_detached_head {
	test -n $quiet || do {
		printf >&2 "$1 > !2 "$1 "
		env GIT_PAGER= git log >&2 -1 --pretty=oneline --abbrev-commit $2 --> !2 -1 --pretty=oneline --abbrev-commit "$2" --
	}
}

if test -z "$branch$newbranch" && test $new_name != $old_name
{
	setglobal detached = $new
	if test -n $oldbranch && test -z $quiet
	{
		setglobal detach_warn = ""Note: moving to \"$new_name\" which isn't a local branch
If you want to create a new branch from this checkout, you may do so
(now or later) by using -b with the checkout command again. Example:
  git checkout -b <new_branch_name>""
	}
} elif test -z $oldbranch && test $new != $old
{
	describe_detached_head 'Previous HEAD position was' $old
}

if test "X$old" = X
{
	if test -z $quiet
	{
		echo >&2 "warning: You appear to be on a branch yet to be born.> !2 "warning: You appear to be on a branch yet to be born."
		echo >&2 "warning: Forcing checkout of $new_name.> !2 "warning: Forcing checkout of $new_name."
	}
	setglobal force = '1'
}

if test $force
{
    git read-tree $v --reset -u $new
} else {
    git update-index --refresh >/dev/null
    git read-tree $v -m -u --exclude-per-directory=.gitignore $old $new || shell {
	match "$merge,$v" {
	with ,*
		exit 1 
	with 1,
		 # quiet
	with *
		echo >&2 "Falling back to 3-way merge...> !2 "Falling back to 3-way merge..." 
	}

	# Match the index to the working tree, and do a three-way.
	git diff-files --name-only | git update-index --remove --stdin &&
	setglobal work = $[git write-tree] &&
	git read-tree $v --reset -u $new || exit

	eval GITHEAD_$new='${new_name:-${branch:-$new}}' &&
	eval GITHEAD_$work=local &&
	export GITHEAD_$new GITHEAD_$work &&
	git merge-recursive $old -- $new $work

	# Do not register the cleanly merged paths in the index yet.
	# this is not a real merge before committing, but just carrying
	# the working tree changes along.
	setglobal unmerged = $[git ls-files -u]
	git read-tree $v --reset $new
	match $unmerged {
	with ''	
	with *
		shell {
			setglobal z40 = '0000000000000000000000000000000000000000'
			echo $unmerged |
			sed -e 's/^[0-7]* [0-9a-f]* /'"0 $z40 /"
			echo $unmerged
		} | git update-index --index-info
		
	}
	exit 0
    }
    setglobal saved_err = $Status
    if test $saved_err = 0 && test -z $quiet
    {
	git diff-index --name-status $new
    }
    shell {exit $saved_err}
}

#
# Switch the HEAD pointer to the new branch if we
# checked out a branch head, and remove any potential
# old MERGE_HEAD's (subsequent commits will clearly not
# be based on them, since we re-set the index)
#
if test "$Status" -eq 0 {
	if test $newbranch {
		git branch $track $newbranch_log $newbranch $new_name || exit
		setglobal branch = $newbranch
	}
	if test -n $branch
	{
		setglobal old_branch_name = $[expr "z$oldbranch" : 'zrefs/heads/\(.*\)]
		env GIT_DIR=$GIT_DIR git symbolic-ref -m "checkout: moving from $(old_branch_name:-$old) to $branch" HEAD "refs/heads/$branch"
		if test -n $quiet
		{
			true	# nothing
		} elif test "refs/heads/$branch" = $oldbranch
		{
			echo >&2 "Already on branch \"$branch> !2 "Already on branch \"$branch\""
		} else {
			echo >&2 "Switched to$(newbranch:+ a new) branch \"$branch> !2 "Switched to${newbranch:+ a new} branch \"$branch\""
		}
	} elif test -n $detached
	{
		setglobal old_branch_name = $[expr "z$oldbranch" : 'zrefs/heads/\(.*\)]
		git update-ref --no-deref -m "checkout: moving from $(old_branch_name:-$old) to $arg" HEAD $detached ||
			die "Cannot detach HEAD"
		if test -n $detach_warn
		{
			echo >&2 $detach_warn> !2 "$detach_warn"
		}
		describe_detached_head 'HEAD is now at' HEAD
	}
	rm -f "$GIT_DIR/MERGE_HEAD"
} else {
	exit 1
}

# Run a post-checkout hook
if test -x "$GIT_DIR"/hooks/post-checkout {
	"$GIT_DIR"/hooks/post-checkout $old $new 1
}