Only copy once even if the first matched src:dest pair appears more than once.

# <dest file> is relative to $(PRODUCT_OUT), so it should look like,

# e.g., "system/etc/file.xml".

# The filter part means "only eval the copy-one-file rule if this

# src:dest pair is the first one to match %:dest"

# src:dest pair is the first one to match the same dest"

unique_product_copy_files_destinations := $(sort \

    $(foreach cf,$(PRODUCT_COPY_FILES), $(call word-colon,2,$(cf))))

$(foreach cf,$(PRODUCT_COPY_FILES), \

    $(eval _src := $(call word-colon,1,$(cf))) \

    $(eval _dest := $(call word-colon,2,$(cf))) \

    $(if $(filter $(unique_product_copy_files_destinations),$(_dest)), \

        $(eval _fulldest := $(call append-path,$(PRODUCT_OUT),$(_dest))) \

  $(if $(filter $(_src):$(_dest),$(firstword $(filter %:$(_dest),$(PRODUCT_COPY_FILES)))), \

    $(eval $(call copy-one-file,$(_src),$(_fulldest))),) \

        $(eval $(call copy-one-file,$(_src),$(_fulldest))) \

        $(eval ALL_DEFAULT_INSTALLED_MODULES += $(_fulldest)) \

 )

        $(eval unique_product_copy_files_destinations := $(filter-out $(_dest), \

            $(unique_product_copy_files_destinations)))))

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# docs/index.html