[PATCH for 7.4.0] conf: Avoid double indentation of <metadata/> element

[Bjoern Walk]

Bjoern Walk <bwalk at linux.ibm.com> [2021-05-25, 11:01AM +0200]:
> Michal Privoznik <mprivozn at redhat.com> [2021-05-25, 09:32AM +0200]:
> > There was a recent change in libxml2 that caused a trouble for
> > us. To us, <metadata/> in domain or network XMLs are just opaque
> > value where management application can store whatever data it
> > finds fit. At XML parser/formatter level, we just make a copy of
> > the element during parsing and then format it back. For
> > formatting we use xmlNodeDump() which allows caller to specify
> > level of indentation. Previously, the indentation was not
> > applied onto the very first line, but as of v2.9.12-2-g85b1792e
> > libxml2 is applying indentation also on the first line.
> > 
> > This does not work well with out virBuffer because as soon as we
> > call virBufferAsprintf() to append <metadata/> element,
> > virBufferAsprintf() will apply another level of indentation.
> > 
> > Instead of version checking, let's skip any indentation added by
> > libxml2 before virBufferAsprintf() is called.
> > 
> > Note, the problem is only when telling xmlNodeDump() to use
> > indentation, i.e. level argument is not zero. Therefore,
> > virXMLNodeToString() which also calls xmlNodeDump() is safe as it
> > passes zero.
> > 
> > Signed-off-by: Michal Privoznik <mprivozn at redhat.com>
> 
> Tested-by: Bjoern Walk <bwalk at linux.ibm.com>
> 
> But like Daniel said, this now breaks for older libxml2 versions.

Ah, I also misread this. All is fine with both libxml2 v2.9.12 and
earlier.

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