Fix tag sorting in PlotWalk
By deferring tag sorting until the commit is produced by the walker
we can avoid an infinite loop that was triggered by trying to sort
tags while allocating a commit. This also avoids needing to look
at commits which aren't going to be produced in the result.
Bug: 321103
Change-Id: I25acc739db2ec0221a50b72c2d2aa618a9a75f37
Reviewed-by: Mathias Kinzler <mathias.kinzler@sap.com>
Reviewed-by: Christian Halstrick <christian.halstrick@sap.com>
Signed-off-by: Shawn O. Pearce <spearce@spearce.org>