git: Add GitattributesSupportReadingFromHead flag
Git 2.43.0 starts supporting reading gitattributes from HEAD reference. This is a required feature for us to get rid of gitattributes-related RPCs.
We are adding a GitattributesSupportReadingFromHead flag to check
if current git version is above or equal 2.43.0.
Closes #5720 (closed)
Edited by Eric Ju