regenerate-workflow

#!/bin/bash
set -euo pipefail

devel="$(dirname "$0")"

main() {
    local in out

    if [[ "$1" == *.in ]]; then
        in="$1"
        out="${1%.in}"
    else
        in="$1.in"
        out="$1"
    fi

    local generated=0
    echo "generating $out"

    if git-unmerged "$in"; then
        echo "error: input file $in is unmerged; please resolve conflicts first" >&2
        exit 1
    fi

    if [[ -f "$in" ]]; then
        generated=1
        "$devel"/explode-yaml < "$in" > "$out" &
    fi

    if git-tracked "$in"; then
        generated=1
        "$devel"/explode-yaml \
            < <(git cat-file blob :"$in") \
            > >(git-add-stdin-as "$out") \
            &
    fi

    wait

    if [[ "$generated" -eq 0 ]]; then
        echo "error: input file $in neither exists on disk nor is it tracked by git" >&2
        exit 1
    fi
}

git-unmerged() {
    # See git-ls-files(1) and git-read-tree(1) for more details on what we're
    # reading here from Git's index.  The gist of it is that when a file X is
    # unmerged, it will show up in the index as three entries with the third
    # field (stage) being 1, 2, and 3:
    #
    #   100644 78981922613b2afb6025042ff6bd878ac1994e85 1 X
    #   100644 d00491fd7e5bb6fa28c517a0bb32b8b506539d4d 2 X
    #   100644 0cfbf08886fca9a91cb753ec8734c84fcbe52c9f 3 X
    #
    # In a normal state, i.e. without merge conflicts or after conflicts have
    # been resolved and recorded, then it shows up as a single entry where
    # stage is 0:
    #
    #   100644 78981922613b2afb6025042ff6bd878ac1994e85 0 X
    #
    git ls-files --stage -z -- "$1" | while read -rd $'\0' mode object stage path; do
        if [[ "$stage" != 0 ]]; then
            return 0
        fi
    done
    return 1
}

git-tracked() {
    git ls-files --stage --error-unmatch -- "$1" >/dev/null 2>&1
}

git-add-stdin-as() {
    # Stages the contents on stdin as the given path in Git's index, without
    # touching the working tree.
    #
    # Originally written for <https://github.com/nextstrain/cli/blob/25075fae/devel/release>.
    local path="$1"
    local repo_path mode object

    # Convert filesystem $path to a canonicalized path from the root of the
    # repo.  This is required for the commands below.
    repo_path="$(git ls-files --full-name --error-unmatch -- "$path")"

    # Use existing mode (e.g. 100644)
    mode="$(git ls-tree --format "%(objectmode)" HEAD :/"$repo_path")"

    # Create new object in git's object database from the contents on stdin.
    # Using --path ensures that any filters (e.g. eol textconv or otherwise)
    # that would apply to $path are applied to the contents on stdin too.
    object="$(git hash-object -w --stdin --path "$repo_path")"

    # Stage the new object as an update to $path (as if with `git add` after
    # actually modifying $path).
    git update-index --cacheinfo "$mode,$object,$repo_path"
}

main "$@"