Add a parallel-capable linter script (*nix)

lint.sh

@@ -0,0 +1,74 @@
+#!/bin/sh
+
+# Runs clang-format on all *.cpp/*.h/*.json files in the project, excluding builds/
+FILE_TYPES="*.cpp *.h *.json"
+EXCLUDED="*/builds/*"
+
+# Make sure we have a clang-format to use.
+# Prefer any clang-format already in the user's $PATH.
+# PATH=$PATH:/usr/bin/
+which -s clang-format || (
+    echo Unable to find clang-format in \$PATH.
+    exit 1
+)
+
+# parse arguments
+while [ "$1" != "" ]; do
+    case $1 in
+        -j | --jobs )
+            shift
+            JOBS="$1"
+            ;;
+        * )
+            echo "Usage: lint.sh [-j|--jobs <NUM_JOBS>]"
+            echo "    If -j is not specified, NUM_JOBS defaults to the number of CPU threads."
+            exit 1
+            ;;
+    esac
+    shift
+done
+
+# Figure out how parallel we're gonna be
+# default to simple single-threaded xargs
+EXECUTOR=xargs
+if [ "$JOBS" != "1" ]; then
+    # if xargs supports parallelism, use that
+    if (echo foo bar | xargs -lkj -P 0$JOBS true 2>/dev/null); then
+        # prefix the $JOBS with 0 so that unspecified JOBS becomes "0" and specified becomes "02" which is still valid
+        # -n 1 so that xargs doesn't simply collect all the args into one job and break parallelism regardless
+        EXECUTOR="xargs -P 0$JOBS -n 1"
+    # if xargs doesn't support it, see if we can use GNU parallel
+    elif which -s parallel; then
+        # -X to spread the parameters evenly among jobs
+        EXECUTOR="parallel -X"
+        # if JOBS is explicitly set, add it (don't use 0-prefix trick; it triggers some buggy behavior in the "-j 0" case)
+        if [ "$JOBS" != "" ]; then
+            EXECUTOR="$EXECUTOR -j $JOBS"
+        fi
+    # if nothing supports parallelism, warn if the user appears to expect it
+    elif [ "$JOBS" != "" ]; then
+        echo "Warning: Parallel jobs specified, but installed xargs does not support -P and GNU parallel not found. Defaulting to single-threaded." >&2
+    fi
+fi
+
+# takes the FILE_TYPES and EXCLUDED vars and concats them into find parameters
+function path_args() {
+    for i in $1; do
+        echo -path "$i" -or
+    done
+}
+
+# finally, run the job
+find .                              \
+    -type f                         \
+    \(                              \
+        $(path_args "$FILE_TYPES")  \
+        -false                      \
+    \)                              \
+    -not \(                         \
+        $(path_args "$EXCLUDED")    \
+        -false                      \
+    \)                              \
+    -print0                         |
+# pipe the file list into the executor (xargs or parallel) to run clang-format
+$EXECUTOR --null clang-format -i