[PATCH][RESEND] checkpatch: Add warning for p0-patches

[Wolfram Sang]

Some people work internally with -p0-patches which has the danger that
one forgets to convert them to -p1 before mainlining. Bitten myself and
seen p0-patches in mailing lists occasionally, this patch adds a warning
to checkpatch.pl in case a patch is -p0. If you really want, you can
fool this check to generate false positives, this is why it just spits a
warning. Making the check 100% proof is trickier than it looks, so let's
start with a version which catches the cases of real use.

Signed-off-by: Wolfram Sang <w.sang@xxxxxxxxxxxxxx>
---
 scripts/checkpatch.pl |    8 +++++++-
 1 files changed, 7 insertions(+), 1 deletions(-)

diff --git a/scripts/checkpatch.pl b/scripts/checkpatch.pl
index f88bb3e..dae5854 100755
--- a/scripts/checkpatch.pl
+++ b/scripts/checkpatch.pl
@@ -1051,6 +1051,7 @@ sub process {
 	my $in_comment = 0;
 	my $comment_edge = 0;
 	my $first_line = 0;
+	my $p1_prefix = '';
 
 	my $prev_values = 'E';
 
@@ -1196,7 +1197,12 @@ sub process {
 		# extract the filename as it passes
 		if ($line=~/^\+\+\+\s+(\S+)/) {
 			$realfile = $1;
-			$realfile =~ s@^[^/]*/@@;
+			$realfile =~ s@^([^/]*)/@@;
+
+			$p1_prefix = $1;
+			if ($tree && -e "$root/$p1_prefix") {
+				WARN("Patch prefix '$p1_prefix' exists. Is it maybe a p0-patch?\n");
+			}
 
 			if ($realfile =~ m@^include/asm/@) {
 				ERROR("do not modify files in include/asm, change architecture specific files in include/asm-<architecture>\n" . "$here$rawline\n");
-- 
1.5.6.5

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