[OE-core] what is meaning of "SRC_URI_append_whatever +=" ??

[Robert P. J. Day]

  still perusing the very basics of oe-core and grepping madly, came
across the following oddity:

$ grep -r SRC_URI_append *
... snip ...
bitbake/doc/manual/usermanual.xml:SRC_URI_append_1.0.7+ = "file://some_patch_which_the_new_versions_need.patch;patch=1"</screen></para>
meta/recipes-support/gmp/gmp_5.0.4.bb:SRC_URI_append += "file://use-includedir.patch \
meta/recipes-support/libcroco/libcroco_0.6.3.bb:SRC_URI_append = " file://croco.patch;apply=yes "
... snip ...

  AIUI, there are two (common) variations for extending SRC_URI.  the
straightforward unconditional way:

  SRC_URI += ... blah blah ...

or if you need to make it conditional, then there's

  SRC_URI_append_thingy = "whatever"

so what's with the latter two entries above?

meta/recipes-support/gmp/gmp_5.0.4.bb:SRC_URI_append += "file://use-includedir.patch \
meta/recipes-support/libcroco/libcroco_0.6.3.bb:SRC_URI_append = " file://croco.patch;apply=yes "

  is there some subtlety i'm missing here?  why would one ever use
either of:

  SRC_URI_append += "..."               (looks redundant)
  SRC_URI_append = "..."                (why not just SRC_URI +=?)

can i just assume those are typoes?

rday

-- 

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Robert P. J. Day                                 Ottawa, Ontario, CANADA
                        http://crashcourse.ca

Twitter:                                       http://twitter.com/rpjday
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