[flow routing] Can tempslope be set when x<1 rather than x<=2?

[dvalters]

This is the only place in the code where we check the leftmost + 2 grid cells to set tempslope, it would make it easier for the libgeodecomp refactor if this was consistent on all edges of the model domain.

Perhaps it is some legacy code from an older version of the CAESAR code?

HAIL-CAESAR/src/catchmentmodel/LSDCatchmentModel.cpp

Line 2348 in b6454bd

if (x <= 2) tempslope = 0 - edgeslope;

It means that in libgeodecomp, there is lots of complicated "edge" cases:

HAIL-CAESAR/src/catchmentmodel/LSDCatchmentModel.cpp

Lines 116 to 125 in 634bcfc

	// must still figure out best way to accumulate total across cells during update executed by LibGeodecomp
	switch(celltype){
	case INTERNAL:
	case EDGE_WEST_INNER:
	case EDGE_NORTH_INNER:
	case CORNER_NW_INNER:
	case CORNER_NW_XPLUS1:
	case CORNER_NW_YPLUS1:
	case CORNER_NE_YPLUS1:
	case CORNER_SW_XPLUS1:

Which make for lots of case statements

Try running the standard test with this changed to x<=1 and run standard case. (Arno and I could not see a reason why this wouldbe necessary at first glance.)