support `b path: path_expr` #452

Job	Run time
ruby-versions / Generate Ruby versions	3s
test (3.4)	56s
test (3.3)	58s
test (3.2)	55s
test (3.0)	57s
test (head)	55s
test (3.1)	50s
test (debug)	1m 17s
	6m 51s

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