share/msysGit/post-checkout-hook

#!/bin/sh

# This post-checkout hook is meant to be installed in msysGit's root repository.
#
# The problem:
#	Windows does not allow deleting or overwriting files that are in use.
#	Concretely, it does not allow msysGit's shell to call Git to update
#	msys-1.0.dll, because the shell still uses it.
#
# The symptoms:
#	Directly after a checkout (as is the case when this hook is called),
#	some files that should have been changed (i.e. that are in the output
#	of 'git diff --name-only $old..$new') are marked modified, i.e. the
#	command 'git diff-files --quiet -- $files' fails.
#
# The solution:
#	We copy a fresh /bin/sh.exe and /bin/msys-1.0.dll into a temporary
#	directory, add a script to that directory that will add the PATH back
#	so we can use the Git commands (which are unaffected by the issue, as
#	they are neither MSys programs nor are they tracked), and then fixes
#	the issue.
#
#	Finally, we add a shortcut on the desktop so that it is easy for the
#	user to start after closing all msysGit windows.

die () {
	echo "$*" >&2
	exit 1
}

test "$3" != 1 && exit
test "$1" = "$2" && exit
MODIFIED="$(cd ./$(git rev-parse --show-cdup) &&
		git diff --ignore-submodules --name-only -z "$1".."$2" |
		xargs -0r git ls-files --modified)"
test -z "$MODIFIED" && exit
cd /share/msysGit || exit 0 # called from tmproot

mkdir -p tmproot/bin tmproot/etc &&
echo "$MODIFIED" > tmproot/etc/modifiedFiles &&
make create-shortcut.exe > /dev/null &&
cp /bin/{sh.exe,msys-1.0.dll,git.exe,cat.exe,rm.exe,xargs.exe} \
	/mingw/bin/{libcurl-4.dll,libiconv2.dll} tmproot/bin/ &&
cat > tmproot/etc/profile << \EOF &&
# cd to msysGit root
cd "$(pwd -W)"/../../../..

# add original msysGit PATH
export PATH=/bin:"$(pwd)/bin:$(pwd)/mingw/bin"

prompt_and_exit () {
	echo "<Press Enter to close this window>" >&2
	read line
	exit "$1"
}

die () {
	printf '\n' >&2
	echo "$*" >&2
	prompt_and_exit 1
}

# Try to update files marked 'modified'
test -s /etc/modifiedFiles && {
	echo "Trying to finish checkout" >&2
	cat /etc/modifiedFiles |
	tr "\n" "\0" |
	xargs -0r git checkout -- ||
	die "Please close _all_ msysGit instances and run this shortcut again"
	test -z "$(cat /etc/modifiedFiles |
		tr "\n" "\0" |
		xargs -0r git diff --ignore-submodules --name-only)" ||
	die "At least one file could not be updated; is msysGit still running?"
}

echo "Everything up-to-date"
test -f /etc/linkfile && rm -f "$(cat /etc/linkfile)"
prompt_and_exit 0
EOF
echo "$USERPROFILE/Desktop/finish-checkout.lnk" > tmproot/etc/linkfile &&
command=sh.exe &&
arguments="--login -i" &&
if test -n "$COMMONPROGRAMW6432"
then
	arguments="//c $command $arguments" &&
	command="$WINDIR"\\SysWOW64\\cmd.exe && echo "$arguments"
fi &&
./create-shortcut --work-dir "$(cd tmproot/bin && pwd -W)" \
	--icon-file "$(cd ../resources && pwd -W)/msysgitlogo.ico" \
	--arguments "$arguments" \
	"$command" \
	"$(cat tmproot/etc/linkfile)" &&
cat << EOF ||

WARNING!
--------

You appear to have modified files after switching branches.  As Windows has
problems updating files that are in use, the most likely reason is that a
.dll or a .exe file needs to be updated, but that was refused due to a process
locking it.

A shortcut 'finish-checkout' was created on your desktop to help you: quit
all msysGit programs, launch that shortcut, and all should be fixed.
EOF
die "Could not set up temporary MSys root"