Check for docker version

Closes #15.

CHANGELOG.md

@@ -18,6 +18,7 @@
 - Show correct status for apps deployed on servers with missing context ([#99](https://git.autonomic.zone/coop-cloud/abra/issues/99))
 - Search for subcommands in descending order of how many components there are ([#108](https://git.autonomic.zone/coop-cloud/abra/issues/108))
 - Add specific app version checking command (`abra app <app> version`) ([#108](https://git.autonomic.zone/coop-cloud/abra/issues/108))
+- Add docker version check (guestimating < v20 is a bad idea) ([#15](https://git.autonomic.zone/coop-cloud/abra/issues/15))
 
 # abra 0.6.0 (2021-03-17)
 

abra

@@ -476,6 +476,15 @@ require_yq() {
   esac
 }
 
+require_docker_version (){
+  major_version=$(docker version --format "{{.Server.Version}}" | cut -d'.' -f1)
+
+  if [[ "$major_version" -lt 20 ]]; then
+    error "This tool requires Docker v20 or greater. Please upgrade your Docker installation"
+    exit 1
+  fi
+}
+
 # FIXME 3wc: update or remove
 if [ -z "$ABRA_ENV" ] && [ -f .env ] && type direnv > /dev/null 2>&1 && ! direnv status | grep -q 'Found RC allowed true'; then
   error "direnv is blocked, run direnv allow"
@@ -1847,6 +1856,7 @@ sub_network() {
 
 abra() {
   require_bash_4
+  require_docker_version
 
   # TODO (3wc): we either need to do this, or add 'shellcheck disable' all over
   # the place to handle the dynamically-defined vars