[OE-core] what's with "SRC_URI_append +=" in meta/lib/oeqa/selftest/layerappend.py?

[Robert P. J. Day]

  every so often, i run a style-checking script against OE, and i just
noticed this in meta/lib/oeqa/selftest/layerappend.py:


  ... snip ...
  SRC_URI_append = " file://appendtest.txt"       <---

  sysroot_stage_all_append() {
        install -m 644 ${WORKDIR}/appendtest.txt ${SYSROOT_DESTDIR}/
  }

  """

    append2 = """
  FILESEXTRAPATHS_prepend := "${THISDIR}/${PN}:"

  SRC_URI_append += "file://appendtest.txt"       <---
  """
  ... snip ...


i'm not sure what's going on in that file, should that second
instance be written with just "=", or is there something more subtle
happening there such that that construct is deliberate?

rday

p.s. i recall from some time back asking about this and while the
initial reaction to writing "..._append += ..." was, "yes, it's
superfluous, but it doesn't hurt," a later comment suggested it
*might* make a difference, in that (i think) using "_append" would
*not* add that leading space, but "+=" *would* add it, so there might
actually be some weird conflict in trying to mix the two.

  thoughts?