Replaces #16262
Replaces #16250
Replaces #14833
This PR first implements a `git check-attr` pipe reader - using `git check-attr --stdin -z --cached` - taking account of the change in the output format in git 1.8.5 and creates a helper function to read a tree into a temporary index file for that pipe reader.
It then wires this in to the language stats helper and into the git diff generation.
Files which are marked generated will be folded by default.
Fixes #14786
Fixes #12653
`enry.IsVendor` is kinda slow as it simply iterates across all regexps.
This PR ajdusts the regexps to combine them to make this process a
little quicker.
Related #15143
Signed-off-by: Andrew Thornton <art27@cantab.net>
Move langauge detection to separate module to be more reusable
Add option to disable vendored file exclusion from file search
Allways show all language stats for search
