* More efficiently parse shas for shaPostProcessor
The shaPostProcessor currently repeatedly calls git rev-parse --verify on both backends
which is fine if there is only one thing that matches a sha - however if there are
multiple things then this becomes wildly inefficient.
This PR provides functions for both backends which are much faster to use.
Fix#16092
* Add ShaExistCache to RenderContext
Signed-off-by: Andrew Thornton <art27@cantab.net>
Co-authored-by: 6543 <6543@obermui.de>
Josef Fröhle
Lunny Xiao