Re: [PATCH 0/2] check-attr: add support to work with revisions

On Tue, Dec 06, 2022 at 11:37:34AM +0100, Karthik Nayak wrote:

I haven't looked at the patches below yet, so take my $.02 with a grain of salt, but I have definitely wished for something like this in the past.

When scripting around to figure out which files at a given revision are affected by a given attribute, I will often have to resort to writing something like this when working in a bare repository:

  for repo in $LIST_OF_REPOS
  do
    export GIT_DIR="$repo"

    index="$(mktemp ...)"
		git read-tree --index-output="$index" HEAD 2>/dev/null || continue

    git ls-tree -rz --name-only HEAD |
    GIT_INDEX_FILE="$index" git check-attr --cached --stdin -z $attr |
    ruby -e '
      print $stdin.readlines.join.split("\0").
        each_slice(3).
        select { |path, _, val| val != "unspecified" && val != "unset" }.
        map(&:first).join("\0")
    '
  done

Which is just kind of gross.

I had at one point when writing the above script wished for a '--blob' source option to check-attr. That might be sensible, but I think being able to read from an arbitrary revision (looking at all of the relevant .gitattributes file(s) recursively throughout the tree) is even more useful, since it allows you to accurately construct the attributes state in its entirety.

Anyway, my point is that I think that this is a useful feature, and one that I (and I suspect other users, too) have wished for frequently in the past.

Thanks, Taylor