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[FEATURE][processing] Add new algorithm "Detect Dataset Changes"

This algorithm compares two vector layers, and determines which features
are unchanged, added or deleted between the two. It is designed for comparing
two different versions of the same dataset.

When comparing features, the original and revised feature geometries will be
compared against each other. Depending on the Geometry Comparison Behavior setting,
the comparison will either be made using an exact comparison (where geometries must
be an exact match for each other, including the order and count of vertices) or a
topological comparison only (where are geometries area considered equal if all of
the their component edges overlap. E.g. lines with the same vertex locations but
opposite direction will be considered equal by this method). If the topological
comparison is selected then any z or m values present in the geometries will not
be compared.

By default, the algorithm compares all attributes from the original and revised
features. If the Attributes to Consider for Match parameter is changed, then only
the selected attributes will be compared (e.g. allowing users to ignore a timestamp
or ID field which is expected to change between the revisions).

If any features in the original or revised layers do not have an associated geometry,
then care must be taken to ensure that these features have a unique set of
attributes selected for comparison. If this condition is not met, warnings will be
raised and the resultant outputs may be misleading.

The algorithm outputs three layers, one containing all features which are considered
to be unchanged between the revisions, one containing features deleted from the
original layer which are not present in the revised layer, and one containing features
add to the revised layer which are not present in the original layer.
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nyalldawson committed Dec 31, 2019
1 parent c304eb5 commit 8c8d48bb8fe82ef8654dd65233e3265f4c3e524e
@@ -43,6 +43,7 @@ SET(QGIS_ANALYSIS_SRCS

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