Improve ergonomics of check_rust_formatting.sh. (pantsbuild#5656)

It now works like `isort.sh`, accepting a -f flag to fix formatting.

build-support/bin/check_rust_formatting.sh

@@ -1,24 +1,77 @@
 #!/usr/bin/env bash
 
-REPO_ROOT="$(cd $(dirname "${BASH_SOURCE[0]}") && cd ../.. && pwd -P)"
+REPO_ROOT="$(git rev-parse --show-toplevel)"
 source "${REPO_ROOT}/build-support/bin/native/bootstrap.sh"
 
+function usage() {
+  echo "Checks formatting of rust files, optionally fixing mis-formatted files."
+  echo
+  echo "Usage: $0 (-h|-f)"
+  echo " -h    print out this help message"
+  echo " -f    instead of erroring on files with bad formatting, fix those files"
+
+  if [[ -n "$@" ]]; then
+    echo
+    echo "$@"
+  fi
+}
+
+write_mode=diff
+
+while getopts "hf" opt; do
+  case ${opt} in
+    h)
+      usage
+      exit 0
+      ;;
+    f)
+      write_mode=overwrite
+      ;;
+    *)
+      usage "Unrecognized arguments."
+      exit 1
+      ;;
+  esac
+done
+
 ensure_native_build_prerequisites >/dev/null
 
-files=( $(find "${NATIVE_ROOT}" -name '*.rs' -not -wholename '*/bazel_protos/*' -not -wholename '*/target/*') "${NATIVE_ROOT}/process_execution/bazel_protos/src/verification.rs" )
-cmd=( "${CARGO_HOME}/bin/rustfmt" --config-path="${NATIVE_ROOT}/rustfmt.toml" )
+cmd=(
+  "${CARGO_HOME}/bin/rustfmt"
+  --config-path="${NATIVE_ROOT}/rustfmt.toml"
+)
+
+files=(
+  $(find "${NATIVE_ROOT}" \
+      -name '*.rs' -not -wholename '*/bazel_protos/*' -not -wholename '*/target/*')
+  "${NATIVE_ROOT}/process_execution/bazel_protos/src/verification.rs"
+)
 
-bad_files=( $(${cmd[*]} ${files[*]} --write-mode=diff 2>/dev/null | awk '$0 ~ /^Diff in/ {print $3}' | sort -u ; exit ${PIPESTATUS[0]}) )
+bad_files=(
+  $(
+    ${cmd[*]} --write-mode=${write_mode} ${files[*]} 2>/dev/null | \
+      awk '$0 ~ /^Diff in/ {print $3}' | \
+      sort -u
+     exit ${PIPESTATUS[0]}
+  )
+)
 case $? in
   4)
-    echo >&2 "Some rust files were incorrectly formatted. Run \`${cmd[*]} --write-mode=overwrite ${bad_files[*]}\` to reformat them."
+    echo >&2 "The following rust files were incorrectly formatted, run \`$0 -f\` to reformat them:"
+    for bad_file in ${bad_files[*]}; do
+      echo >&2 ${bad_file}
+    done
     exit 1
     ;;
   0)
     exit 0
     ;;
   *)
-    echo >&2 "An error occured while checking the formatting of rust files. Try running \`${cmd[*]} --write-mode=diff ${files[*]}\` to investigate. Its error is:"
+    cat << EOF >&2
+An error occurred while checking the formatting of rust files.
+Try running \`${cmd[*]} --write-mode=diff ${files[*]}\` to investigate.
+Its error is:
+EOF
     ${cmd[*]} --write-mode=diff ${files[*]} >/dev/null
     exit 1
     ;;