[shell] Extend powerful cd and move it to its own file

Add support for ‘.../directory’ paths in the powerful cd and move it to
its own file.

bin/pcd.sh

@@ -0,0 +1,73 @@
+# shellcheck shell=sh disable=SC2164
+
+cd() {
+	case "$#:$1" in
+	1:-h)
+		cat <<EOF
+cd                                     Move to home directory.
+cd -P                                  Resolve all symbolic links in \$PWD.
+cd [-L | -P | --] <target>             Move to given <target>.
+cd [-L | -P | --] <target> <cmd> ...   Run <cmd> in the given <target>.
+
+<target> can be:
+  -           Move to directory stored in \$OLDPWD
+  .../<path>  Move to a sibling/cusing directory <path>; this will iterate
+              up the directories until <path> is located
+  <file>      Move to directory containing the file
+  <dir>       Move to given directory
+EOF
+		;;
+	0:)
+		command cd
+		;;
+	1:-[LP])
+		command cd "$1" "${PWD}"
+		;;
+	1:*)
+		_cd_do -L "$1"
+		;;
+	2:--)
+		_cd_do -L "$2"
+		;;
+	2:-[LP])
+		_cd_do "$1" "$2"
+		;;
+	*)
+		if [ "$1" = -- ]; then
+			shift
+			set -- -L "$@"
+		elif [ "$1" != -P ]; then
+			set -- -L "$@"
+		fi
+		( _cd_do "$1" "$2" && shift 2 && exec "$@" )
+	esac
+}
+
+_cd_do() {
+	case "$2" in
+	-)
+		:
+		;;
+	.../*)
+		set -- "$1" "$2" .. "${2#*/}" "$(stat -Lc%d:%i /)"
+		while
+			if [ -e "$3/$4" ]; then
+				set -- "$1" "$3/$4"
+				if ! [ -d "$2" ]; then
+					set -- "$1" "$(dirname "$2")"
+				fi
+				false
+			else
+				test "$5" != "$(stat -Lc%d:%i "$3")"
+			fi
+		do
+			set -- "$1" "$2" "../$3" "$4" "$5"
+		done
+		;;
+	*)
+		if [ -e "$2" ] && ! [ -d "$2" ]; then
+			set -- "$1" "$(dirname "$2")"
+		fi
+	esac
+	command cd "$1" -- "$2"
+}

sh/shellrc

@@ -138,54 +138,12 @@ if echo foo | grep --color=auto foo >/dev/null 2>/dev/null; then
 fi
 
 # Powerful cd
-_cd_do() {
-	if [ x"$2" != x- ] && [ -e "$2" ] && ! [ -d "$2" ]; then
-		set -- "$1" "$(dirname "$2")"
-	fi
-	command cd "$1" -- "$2" || return
-}
-
-cd() {
-	case "$#:$1" in
-	1:-h)
-		cat <<EOF
-cd
-    Move to home directory.
-cd -P
-    Resolve all symbolic links in \$PWD.
-cd [-P | --] (<dir> | <file> | -)
-    Move to <dir>, dirname(<file>), or \$OLDPWD; -P resolves all symlinks.
-cd [-P | --] (<dir> | <file> | -) <command> [<args> ...]
-    Run <command> in the directory and then come back.
-EOF
-		;;
-	0:|1:--)
-		command cd || return
-		;;
-	1:-P)
-		command cd -P "${PWD}" || return
-		;;
-	1:*)
-		_cd_do "-L" "$1"
-		;;
-	2:--)
-		_cd_do "-L" "$2"
-		;;
-	2:-P)
-		_cd_do "-P" "$2"
-		;;
-	*)
-		if [ "$1" = -- ]; then
-			shift
-			set -- -L "$@"
-		elif [ "$1" != -P ]; then
-			set -- -L "$@"
-		fi
-		( _cd_do "$1" "$2" && shift 2 && exec "$@" )
-	esac
-}
-# Bash interprets ’-=…’ as a flag so ‘--’ is needed but BusyBox complains about
-# it so silence the warning.
+if [ -e ~/.local/bin/pcd.sh ]; then
+	# shellcheck source=../bin/pcd.sh
+	. ~/.local/bin/pcd.sh
+fi
+# Bash interprets ’-=…’ as a flag so ‘--’ is needed
+# but BusyBox complains about it so silence the warning.
 alias -- -='cd -' 2>/dev/null
 
 alias '+=git add'