Add commit hook and make the verification customizable.

There are three hooks:

    - 'pre-commit' is given an opportunity to inspect what is
      being committed, before we invoke the EDITOR for the
      commit message;

    - 'commit-msg' is invoked on the commit log message after
      the user prepares it;

    - 'post-commit' is run after a successful commit is made.

The first two can interfere to stop the commit.  The last one is
for after-the-fact notification.

The earlier built-in commit checker is now moved to pre-commit.

Signed-off-by: Junio C Hamano <junkio@cox.net>

3 files changed, 82 insertions, 0 deletions

diff --git a/templates/hooks--commit-msg b/templates/hooks--commit-msg
new file mode 100644
index 000000000..029f897c4
--- /dev/null
+++ b/templates/hooks--commit-msg
@@ -0,0 +1,14 @@
+#!/bin/sh
+#
+# An example hook script to check the commit log message.
+# Called by git-commit-script with one argument, the name of the file
+# that has the commit message.  The hook should exit with non-zero
+# status after issuing an appropriate message if it wants to stop the
+# commit.  The hook is allowed to edit the commit message file.
+#
+# To enable this hook, make this file executable.
+
+# This example catches duplicate Signed-off-by lines.
+
+test "" = "$(grep '^Signed-off-by: ' "$1" |
+	 sort | uniq -c | sed -e '/^[ 	]*1 /d')"
diff --git a/templates/hooks--post-commit b/templates/hooks--post-commit
new file mode 100644
index 000000000..8be6f34ad
--- /dev/null
+++ b/templates/hooks--post-commit
@@ -0,0 +1,8 @@
+#!/bin/sh
+#
+# An example hook script that is called after a successful
+# commit is made.
+#
+# To enable this hook, make this file executable.
+
+: Nothing
diff --git a/templates/hooks--pre-commit b/templates/hooks--pre-commit
new file mode 100644
index 000000000..cb1c82d55
--- /dev/null
+++ b/templates/hooks--pre-commit
@@ -0,0 +1,60 @@
+#!/bin/sh
+#
+# An example hook script to verify what is about to be committed.
+# Called by git-commit-script with no arguments.  The hook should
+# exit with non-zero status after issuing an appropriate message if
+# it wants to stop the commit.
+#
+# To enable this hook, make this file executable.
+
+# 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.
+perl -e '
+    my $fh;
+    my $found_bad = 0;
+    my $filename;
+    my $reported_filename = "";
+    my $lineno;
+    sub bad_line {
+	my ($why, $line) = @_;
+	if (!$found_bad) {
+	    print "*\n";
+	    print "* You have some suspicious patch lines:\n";
+	    print "*\n";
+	    $found_bad = 1;
+	}
+	if ($reported_filename ne $filename) {
+	    print "* In $filename\n";
+	    $reported_filename = $filename;
+	}
+	print "* $why (line $lineno)\n$line\n";
+    }
+    open $fh, "-|", qw(git-diff-cache -p -M --cached HEAD);
+    while (<$fh>) {
+	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* 	/) {
+		bad_line("indent SP followed by a TAB", $_);
+	    }
+	}
+    }
+    exit($found_bad);
+'
+