Commit message format in contributing guidelines

Add the need to have a commit message with a specific
format to the contributing guidelines. Provide a script
to help enforce commit message style.

Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov>
Reviewed-by: George Melikov <mail@gmelikov.ru>
Signed-off-by: Giuseppe Di Natale <dinatale2@llnl.gov>
Closes #5943

scripts/commitcheck.sh

@@ -0,0 +1,144 @@
+#!/bin/bash
+
+REF="HEAD"
+
+# test a url
+function test_url()
+{
+    url="$1"
+    if ! curl --output /dev/null --max-time 60 \
+		--silent --head --fail "$url" ; then
+        echo "\"$url\" is unreachable"
+        return 1
+    fi
+}
+
+# check for a tagged line
+function check_tagged_line()
+{
+    regex='^\s*'"$1"':\s+\S+\s+\<\S+\>'
+    foundline=$(git log -n 1 "$REF" | egrep -m 1 "$regex")
+    if [ -z "$foundline" ]; then
+        echo "error: missing \"$1\""
+        return 1
+    fi
+
+    return 0
+}
+
+# check for a tagged line and check that the link is valid
+function check_tagged_line_with_url ()
+{
+    regex='^\s*'"$1"':\s+\K(\S+)'
+    foundline=$(git log -n 1 "$REF" | grep -Po "$regex")
+    if [ -z "$foundline" ]; then
+        echo "error: missing \"$1\""
+        return 1
+    fi
+
+    if ! test_url "$foundline"; then
+        return 1
+    fi
+
+    return 0
+}
+
+# check commit message for a normal commit
+function new_change_commit()
+{
+    error=0
+
+    # subject is not longer than 50 characters
+    long_subject=$(git log -n 1 --pretty=%s "$REF" | egrep -m 1 '.{51}')
+    if [ -n "$long_subject" ]; then
+        echo "error: commit subject over 50 characters"
+        error=1
+    fi
+
+    # need a signed off by
+    if ! check_tagged_line "Signed-off-by" ; then
+        error=1
+    fi
+
+    # ensure that no lines in the body of the commit are over 72 characters
+    body=$(git log -n 1 --pretty=%b "$REF" | egrep -m 1 '.{73}')
+    if [ -n "$body" ]; then
+        echo "error: commit message body contains line over 72 characters"
+        error=1
+    fi
+
+    return $error
+}
+
+function is_openzfs_port()
+{
+    # subject starts with OpenZFS means it's an openzfs port
+    subject=$(git log -n 1 --pretty=%s "$REF" | egrep -m 1 '^OpenZFS')
+    if [ -n "$subject" ]; then
+        return 0
+    fi
+
+    return 1
+}
+
+function openzfs_port_commit()
+{
+    # subject starts with OpenZFS dddd
+    subject=$(git log -n 1 --pretty=%s "$REF" | egrep -m 1 '^OpenZFS [[:digit:]]+ - ')
+    if [ -z "$subject" ]; then
+        echo "OpenZFS patch ports must have a summary that starts with \"OpenZFS dddd - \""
+        error=1
+    fi
+
+    # need an authored by line
+    if ! check_tagged_line "Authored by" ; then
+        error=1
+    fi
+
+    # need a reviewed by line
+    if ! check_tagged_line "Reviewed by" ; then
+        error=1
+    fi
+
+    # need a approved by line
+    if ! check_tagged_line "Approved by" ; then
+        error=1
+    fi
+
+    # need ported by line
+    if ! check_tagged_line "Ported-by" ; then
+        error=1
+    fi
+
+    # need a url to openzfs commit and it should be valid
+    if ! check_tagged_line_with_url "OpenZFS-commit" ; then
+        error=1
+    fi
+
+    # need a url to illumos issue and it should be valid
+    if ! check_tagged_line_with_url "OpenZFS-issue" ; then
+        error=1
+    fi
+
+    return $error
+}
+
+if [ -n "$1" ]; then
+    REF="$1"
+fi
+
+# if openzfs port, test against that
+if is_openzfs_port; then
+    if ! openzfs_port_commit ; then
+        exit 1
+    else
+        exit 0
+    fi
+fi
+
+# have a normal commit
+if ! new_change_commit ; then
+    exit 1
+fi
+
+exit 0