script/validate-c: simplify, check everything

Instead of using a complex logic to figure out which files were modified
and checking those, just check all files in the repo (not that we have
many). This serves two purposes:

1. Making sure the formatting is always checked (I suspect it was not
   working as it should).

2. Simplify the script logic (a lot).

While at it, do some other minor improvements:

 - actually show the diff to a user (and rely on diff exit code
   rather than output or the lack thereof);

 - don't create temp files -- use bash here-file instead.

Signed-off-by: Kir Kolyshkin <[email protected]>

script/validate-c

@@ -1,9 +1,7 @@
 #!/bin/bash
 
-source "$(dirname "$BASH_SOURCE")/.validate"
-
 IFS=$'\n'
-files=($(validate_diff --diff-filter=ACMR --name-only -- '*.c' | grep -v '^vendor/' || true))
+files=($(git ls-files '*.c' | grep -v '^vendor/' || true))
 unset IFS
 
 # indent(1): "You must use the ‘-T’ option to tell indent the name of all the typenames in your program that are defined by typedef."
@@ -15,21 +13,16 @@ fi
 
 badFiles=()
 for f in "${files[@]}"; do
-	orig=$(mktemp)
-	formatted=$(mktemp)
-	# we use "git show" here to validate that what's committed is formatted
-	git show "$VALIDATE_HEAD:$f" >${orig}
-	${INDENT} ${orig} -o ${formatted}
-	if [ "$(diff -u ${orig} ${formatted})" ]; then
+	if ! diff -u "$f" <($INDENT -st $f); then
 		badFiles+=("$f")
 	fi
-	rm -f ${orig} ${formatted}
 done
 
 if [ ${#badFiles[@]} -eq 0 ]; then
 	echo 'Congratulations!  All C source files are properly formatted.'
 else
 	{
+		echo
 		echo "These files are not properly formatted:"
 		for f in "${badFiles[@]}"; do
 			echo " - $f"