checkpatch: warn on unnecessary else after return or break

Using an else following a break or return can unnecessarily indent code
blocks.

ie:
	for (i = 0; i < 100; i++) {
		int foo = bar();
		if (foo < 1)
			break;
		else
			usleep(1);
	}

is generally better written as:

	for (i = 0; i < 100; i++) {
		int foo = bar();
		if (foo < 1)
			break;
		usleep(1);
	}

Warn when a bare else statement is preceded by a break or return
indented 1 tab more than the else.

Signed-off-by: Joe Perches <joe@perches.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

scripts/checkpatch.pl

@@ -2342,6 +2342,16 @@ sub process {
 # check we are in a valid C source file if not then ignore this hunk
 		next if ($realfile !~ /\.(h|c)$/);
 
+# check indentation of any line with a bare else
+# if the previous line is a break or return and is indented 1 tab more...
+		if ($sline =~ /^\+([\t]+)(?:}[ \t]*)?else(?:[ \t]*{)?\s*$/) {
+			my $tabs = length($1) + 1;
+			if ($prevline =~ /^\+\t{$tabs,$tabs}(?:break|return)\b/) {
+				WARN("UNNECESSARY_ELSE",
+				     "else is not generally useful after a break or return\n" . $hereprev);
+			}
+		}
+
 # discourage the addition of CONFIG_EXPERIMENTAL in #if(def).
 		if ($line =~ /^\+\s*\#\s*if.*\bCONFIG_EXPERIMENTAL\b/) {
 			WARN("CONFIG_EXPERIMENTAL",