configure: Autodetect docker or podman

README.md

@@ -81,7 +81,7 @@ documentation for setup instructions (e.g. Arch [Podman][arch-podman] /
 
 ```bash
 mkdir ../build && cd ../build
-../proton/configure.sh --container-engine=podman --enable-ccache --build-name=my_build
+../proton/configure.sh --enable-ccache --build-name=my_build
 ```
 
 Running `configure.sh` will create a `Makefile` allowing you to build Proton.
@@ -89,8 +89,9 @@ The scripts checks if containers are functional and prompt you if any
 host-side dependencies are missing. You should run the command from a
 directory created specifically for your build.
 
-The build by default uses Docker, but you can switch to another, compatible
-engine with `--container-engine=<executable_name>`.
+The configuration script tries to discover a working Docker or Podman setup
+to use, but you can force a compatible engine with
+`--container-engine=<executable_name>`.
 
 You can enable ccache with `--enable-cache` flag. This will mount your
 `$CCACHE_DIR` or `$HOME/.ccache` inside the container.

configure.sh

@@ -61,20 +61,21 @@ dependency_afdko() {
 CONTAINER_MOUNT_OPTS=""
 
 check_container_engine() {
-    info "Making sure that the container engine is working."
-    if ! cmd $arg_container_engine run --rm $arg_protonsdk_image; then
-        die "Broken container engine. Please fix your $arg_container_engine setup."
+    stat "Trying $1."
+    if ! cmd $1 run --rm $arg_protonsdk_image; then
+        info "$1 is unable to run the container."
+        return 1
     fi
 
     touch permission_check
-    local inner_uid="$($arg_container_engine run -v "$(pwd):/test$CONTAINER_MOUNT_OPTS" \
+    local inner_uid="$($1 run -v "$(pwd):/test$CONTAINER_MOUNT_OPTS" \
                                             --rm $arg_protonsdk_image \
                                             stat --format "%u" /test/permission_check 2>&1)"
     rm permission_check
 
     if [[ $inner_uid == *"Permission denied"* ]]; then
         err "The container cannot access files. Are you using SELinux?"
-        die "Please read README.md and check your $arg_container_engine setup works."
+        die "Please read README.md and check your $1 setup works."
     elif [ "$inner_uid" -eq 0 ]; then
         # namespace maps the user as root or the build is performed as host's root
         ROOTLESS_CONTAINER=1
@@ -82,7 +83,7 @@ check_container_engine() {
         ROOTLESS_CONTAINER=0
     else
         err "File owner's UID doesn't map to 0 or $(id -u) in the container."
-        die "Don't know how to map permissions. Please check your $arg_container_engine setup."
+        die "Don't know how to map permissions. Please check your $1 setup."
     fi
 }
 
@@ -141,9 +142,20 @@ function configure() {
   fi
 
   if [[ -n "$arg_container_engine" ]]; then
-    check_container_engine
+    check_container_engine "$arg_container_engine" || die "Specified container engine \"$arg_container_engine\" doesn't work"
+  else
+    stat "Trying to find usable container engine."
+    if check_container_engine docker; then
+      arg_container_engine="docker"
+    elif check_container_engine podman; then
+      arg_container_engine="podman"
+    else
+        die "${arg_container_engine:-Container engine discovery} has failed. Please fix your setup."
+    fi
   fi
 
+  stat "Using $arg_container_engine."
+
   ## Write out config
   # Don't die after this point or we'll have rather unhelpfully deleted the Makefile
   [[ ! -e "$MAKEFILE" ]] || rm "$MAKEFILE"
@@ -190,7 +202,7 @@ arg_steamrt="soldier"
 arg_protonsdk_image="registry.gitlab.steamos.cloud/proton/soldier/sdk:0.20211207.0-0"
 arg_no_protonsdk=""
 arg_build_name=""
-arg_container_engine="docker"
+arg_container_engine=""
 arg_docker_opts=""
 arg_relabel_volumes=""
 arg_enable_ccache=""
@@ -291,8 +303,8 @@ usage() {
   "$1" ""
   "$1" "    --build-name=<name>  Set the name of the build that displays when used in Steam"
   "$1" ""
-  "$1" "    --container-engine=<engine> Which container Docker-compatible container engine to use,"
-  "$1" "                                e.g. podman. Defaults to docker."
+  "$1" "    --container-engine=<engine> Which Docker-compatible container engine to use,"
+  "$1" "                                e.g. podman. Tries to do autodiscovery when not specified."
   "$1" ""
   "$1" "    --docker-opts='<options>' Extra options to pass to Docker when invoking the runtime."
   "$1" ""