clang-format: rework "nm-code-format-container.sh" script

Instead of doing the broken `podman run` and `podman start` approach,
build an image ("nm-code-format:f38"), cache it, and use it to run
"nm-code-format.sh" via `podman run`. We should build and keep a
container image, not a container.

The benefit is that this allows to hand over the command line arguments
to "nm-code-format.sh". In particular the "-u" and "-F" options, which
are life savers.

This means,

  $ contrib/scripts/nm-code-format-container.sh -u

works.

Try also

  $ contrib/scripts/nm-code-format-container.sh -h

which tells you that you are running inside the container, and how to
delete/renew the container image.

https://gitlab.freedesktop.org/NetworkManager/NetworkManager/-/merge_requests/1798
(cherry picked from commit a6e085b3e8)

CONTRIBUTING.md

@@ -49,7 +49,7 @@ Coding Style
 
 The formatting is automated using [clang-format](https://clang.llvm.org/docs/ClangFormat.html).
 Run `./contrib/scripts/nm-code-format.sh -i` ([[1]](contrib/scripts/nm-code-format.sh)) to reformat
-the code or run `clang-format` directly.
+the code or run `clang-format` directly. Pass `--help` for the list of options.
 
 As the generated format depends on the version of clang-format, you need to use the
 correct clang-format version. That is basically the version that our [gitlab-ci
@@ -58,6 +58,7 @@ for the "check-tree" test. This is the version from a recent Fedora installation
 
 You may also run `./contrib/scripts/nm-code-format-container.sh` which uses a
 Fedora container with podman and the correct version of clang-format.
+This accepts the same arguments as `./contrib/scripts/nm-code-format.sh`.
 
 You are welcome to not bother and open a merge request with wrong formatting,
 but note that we then will automatically adjust your contribution before

contrib/scripts/nm-code-format-container.sh

@@ -16,36 +16,31 @@ FEDORA_VERSION="$(sed '/^    tier: 1/,/^  - name/!d' .gitlab-ci/config.yml | sed
 
 test -n "$FEDORA_VERSION" || die "Could not detect the Fedora version in .gitlab-ci/config.yml"
 
-PODNAME="nm-code-format-f$FEDORA_VERSION"
+IMAGENAME="nm-code-format:f$FEDORA_VERSION"
 
-RENEW=0
-for a; do
-    case "$a" in
-        -f)
-            RENEW=1
-            ;;
-        *)
-            die "invalid argument \"$a\""
-            ;;
-    esac
-done
+ARGS=( "$@" )
 
-set -x
-
-if [ "$RENEW" == 1 ]; then
-    if podman container exists "$PODNAME" ; then
-        podman rm "$PODNAME"
-    fi
+if ! podman image exists "$IMAGENAME" ; then
+    echo "Building image \"$IMAGENAME\"..."
+    podman build \
+        --squash-all \
+        --tag "$IMAGENAME" \
+        -f <(cat <<EOF
+FROM fedora:$FEDORA_VERSION
+RUN dnf upgrade -y
+RUN dnf install -y git /usr/bin/clang-format
+EOF
+)
 fi
 
-if ! podman container exists "$PODNAME" ; then
-    podman run \
-        --name="$PODNAME" \
-        -v "$DIR:/tmp/NetworkManager:Z" \
-        -w /tmp/NetworkManager \
-        "fedora:$FEDORA_VERSION" \
-        /bin/bash -c 'dnf upgrade -y && dnf install -y git /usr/bin/clang-format && ./contrib/scripts/nm-code-format.sh -i'
-    exit 0
-fi
+CMD=( ./contrib/scripts/nm-code-format.sh "${ARGS[@]}" )
 
-podman start -a "$PODNAME"
+podman run \
+    --rm \
+    --name "nm-code-format-f$FEDORA_VERSION" \
+    -v "$DIR:/tmp/NetworkManager:Z" \
+    -w /tmp/NetworkManager \
+    -e "_NM_CODE_FORMAT_CONTAINER=$IMAGENAME" \
+    -ti \
+    "$IMAGENAME" \
+    "${CMD[@]}"

contrib/scripts/nm-code-format.sh

@@ -65,6 +65,11 @@ usage() {
     printf "    -F|--fast          Same as \`-u HEAD^\`.\n"
     printf "    --show-filenames   Only print the filenames that would be checked/formatted\n"
     printf "    --                 Separate options from filenames/directories\n"
+    if [ -n "${_NM_CODE_FORMAT_CONTAINER+x}" ] ; then
+        printf "\n"
+        printf "Command runs inside container image \"$_NM_CODE_FORMAT_CONTAINER\".\n"
+        printf "Delete/renew image with \`podman rmi \"$_NM_CODE_FORMAT_CONTAINER\"\`.\n"
+    fi
 }
 
 ls_files_exist() {