proot: Add termux-chroot utility script

disabled-packages/proot/build.sh

@@ -16,4 +16,6 @@ termux_step_make_install () {
 
 	mkdir -p $TERMUX_PREFIX/share/man/man1
 	cp $TERMUX_PKG_SRCDIR/doc/proot/man.1 $TERMUX_PREFIX/share/man/man1/proot.1
+
+	cp $TERMUX_PKG_BUILDER_DIR/termux-chroot $TERMUX_PREFIX/bin/
 }

disabled-packages/proot/termux-chroot

@@ -0,0 +1,45 @@
+#!/bin/sh
+
+if [ $# != 0 ]; then
+	echo "termux-chroot: Setup a chroot to mimic a normal Linux file system"
+	echo ""
+	echo "Execute without arguments to run a chroot with traditional file system"
+	echo "hierarchy (having e.g. the folders /bin, /etc and /usr) within Termux."
+	exit
+fi
+
+# For the /system/bin/linker(64) to be found:
+ARGS="-b /system:/system"
+
+# Bind $PREFIX so Termux programs expecting
+# to find e.g. configurations files there work.
+ARGS="$ARGS -b $PREFIX/..:$PREFIX/.."
+
+# Mimic traditional Linux file system hierarchy - /usr:
+ARGS="$ARGS -b $PREFIX:/usr"
+
+# Mimic traditional Linux file system hierarchy - other Termux dirs:
+for f in bin etc lib share tmp var; do
+	ARGS="$ARGS -b $PREFIX/$f:/$f"
+done
+
+# Mimic traditional Linux file system hierarchy- system dirs:
+for f in dev proc; do
+	ARGS="$ARGS -b /$f:/$f"
+done
+
+# Set /home as current directory:
+ARGS="$ARGS --cwd=/home"
+
+# Root of the file system:
+ARGS="$ARGS -r $PREFIX/.."
+
+# Program to execute:
+PROGRAM=/bin/bash
+if [ -x $HOME/.termux/shell ]; then
+	PROGRAM=`readlink -f $HOME/.termux/shell`
+fi
+ARGS="$ARGS $PROGRAM -l"
+
+export HOME=/home
+$PREFIX/bin/proot $ARGS