Update sample pre-commit hook to use "diff --check"

Now "diff --check" can detect not just whitespace errors but also notices
leftover conflict marker lines, we can use it in the sample pre-commit
hook script.

These days the object layer knows about the empty tree object without
actually having one in the repository, so we can run the test even for the
initial commit.

Signed-off-by: Junio C Hamano <gitster@pobox.com>

diff --git a/templates/hooks--pre-commit.sample b/templates/hooks--pre-commit.sample
index 71c10f25f485f4a995f4617a5fa7b0e424fcaae8..0e49279c7f7b805c78f1bc4760a0d1c70a84a0d9 100755 (executable)
--- a/templates/hooks--pre-commit.sample
+++ b/templates/hooks--pre-commit.sample
@@ -7,64 +7,12 @@
 #
 # To enable this hook, rename this file to "pre-commit".
 
-# This is slightly modified from Andrew Morton's Perfect Patch.
-# Lines you introduce should not have trailing whitespace.
-# Also check for an indentation that has SP before a TAB.
-
 if git-rev-parse --verify HEAD 2>/dev/null
 then
-       git-diff-index -p -M --cached HEAD --
+       against=HEAD
 else
-       # NEEDSWORK: we should produce a diff with an empty tree here
-       # if we want to do the same verification for the initial import.
-       :
-fi |
-perl -e '
-    my $found_bad = 0;
-    my $filename;
-    my $reported_filename = "";
-    my $lineno;
-    sub bad_line {
-       my ($why, $line) = @_;
-       if (!$found_bad) {
-           print STDERR "*\n";
-           print STDERR "* You have some suspicious patch lines:\n";
-           print STDERR "*\n";
-           $found_bad = 1;
-       }
-       if ($reported_filename ne $filename) {
-           print STDERR "* In $filename\n";
-           $reported_filename = $filename;
-       }
-       print STDERR "* $why (line $lineno)\n";
-       print STDERR "$filename:$lineno:$line\n";
-    }
-    while (<>) {
-       if (m|^diff --git a/(.*) b/\1$|) {
-           $filename = $1;
-           next;
-       }
-       if (/^@@ -\S+ \+(\d+)/) {
-           $lineno = $1 - 1;
-           next;
-       }
-       if (/^ /) {
-           $lineno++;
-           next;
-       }
-       if (s/^\+//) {
-           $lineno++;
-           chomp;
-           if (/\s$/) {
-               bad_line("trailing whitespace", $_);
-           }
-           if (/^\s* \t/) {
-               bad_line("indent SP followed by a TAB", $_);
-           }
-           if (/^([<>])\1{6} |^={7}$/) {
-               bad_line("unresolved merge conflict", $_);
-           }
-       }
-    }
-    exit($found_bad);
-'
+       # Initial commit: diff against an empty tree object
+       against=4b825dc642cb6eb9a060e54bf8d69288fbee4904
+fi
+
+exec git diff-index --check --cached $against --