Lock CircleCI builds by testing git (any vcs) tags against a regex. I use some git tag suffixes to specify deployment environment, so 1.2.3staging1 will deploy to staging, however it cannot run at the same time as 1.2.3staging2 or 1.2.4staging1.

do-exclusive-with-vsc_tag.sh

#!/usr/bin/env bash

# I've made changes to this script so it supports a --version argument
# which can specify a regular expression for the vcs_tag property on circle
# builds.
#

# sets $branch, $tag, $rest
parse_args() {
    while [[ $# -gt 0 ]]; do
        case $1 in
            -b|--branch) branch="$2" ;;
            -t|--tag) tag="$2" ;;
            -v|--version) version="$2" ;;
            *) break ;;
        esac
        shift 2
    done
    rest=("$@")
}

# reads $branch, $tag, $commit_message
should_skip() {
    if [[ "$version" && "$CIRCLE_TAG" =~ "$version" ]]; then
        echo "Not on $version. Skipping..."
        return 0
    fi

    if [[ "$branch" && "$CIRCLE_BRANCH" != "$branch" ]]; then
        echo "Not on branch $branch. Skipping..."
        return 0
    fi

    if [[ "$tag" && "$commit_message" != *\[$tag\]* ]]; then
        echo "No [$tag] commit tag found. Skipping..."
        return 0
    fi

    return 1
}

# reads $branch, $tag
# sets $jq_prog
make_jq_prog() {
    local jq_filters=""

    if [[ $branch ]]; then
        jq_filters+=" and .branch == \"$branch\""
    fi

    if [[ $tag ]]; then
        jq_filters+=" and (.subject | contains(\"[$tag]\"))"
    fi

    if [[ $version ]]; then
        jq_filters+=" and (.vcs_tag | test(\"${version//\./\\\\.}\"))"
    fi

    jq_prog=".[] | select(.build_num < $CIRCLE_BUILD_NUM and (.status | test(\"running|pending|queued\")) $jq_filters) | .build_num"
}


if [[ "$0" != *bats* ]]; then
set -e
set -u
set -o pipefail

    branch=""
    tag=""
    version=""
    rest=()
    api_url="https://circleci.com/api/v1/project/$CIRCLE_PROJECT_USERNAME/$CIRCLE_PROJECT_REPONAME?circle-token=$CIRCLE_TOKEN&limit=100"

    parse_args "$@"
    commit_message=$(git log -1 --pretty=%B)
    if should_skip; then exit 0; fi
    make_jq_prog

    echo "Checking for running builds..."

    while true; do
        builds=$(curl -s -H "Accept: application/json" "$api_url" | jq "$jq_prog")
        if [[ $builds ]]; then
            echo "Waiting on builds:"
            echo "$builds"
        else
            break
        fi
        echo "Retrying in 5 seconds..."
        sleep 5
    done

    echo "Acquired lock"

    if [[ "${#rest[@]}" -ne 0 ]]; then
        "${rest[@]}"
    fi
fi