Allow whitespace when finding commit messages (#47)

Allow whitespace after the opening tag and before the closing tag that
delimit commit messages in a PR body. Also place the regexp in
multi-line mode and use `^` and `$` to match the start and end of lines
instead of the literal `\r\n` string.

github/github.go

@@ -379,23 +379,32 @@ func (client *Client) commitMessage(pr *github.PullRequest, mergeMethod string)
 			}
 		}
 
-		var r *regexp.Regexp
-		if strings.Contains(pr.GetBody(), "==COMMIT_MSG==") {
-			r = regexp.MustCompile("(?s:(==COMMIT_MSG==\r\n)(.*)(\r\n==COMMIT_MSG==))")
-		} else if strings.Contains(pr.GetBody(), "==SQUASH_MSG==") {
-			r = regexp.MustCompile("(?s:(==SQUASH_MSG==\r\n)(.*)(\r\n==SQUASH_MSG==))")
-		}
-		if r != nil {
-			m := r.FindStringSubmatch(pr.GetBody())
-			if len(m) == 4 {
-				commitMessage = m[2]
-			}
+		if msg, ok := extractMessageOverride(pr.GetBody()); ok {
+			commitMessage = msg
 		}
 	}
 
 	return commitMessage, nil
 }
 
+func extractMessageOverride(body string) (msg string, found bool) {
+	var r *regexp.Regexp
+	if strings.Contains(body, "==COMMIT_MSG==") {
+		r = regexp.MustCompile(`(?sm:(==COMMIT_MSG==\s*)^(.*)$(\s*==COMMIT_MSG==))`)
+	} else if strings.Contains(body, "==SQUASH_MSG==") {
+		r = regexp.MustCompile(`(?sm:(==SQUASH_MSG==\s*)^(.*)$(\s*==SQUASH_MSG==))`)
+	}
+
+	if r != nil {
+		m := r.FindStringSubmatch(body)
+		if len(m) == 4 {
+			msg = strings.TrimSpace(m[2])
+			found = true
+		}
+	}
+	return
+}
+
 func (client *Client) Merge(pr *github.PullRequest) error {
 	logger := client.Logger
 

github/github_test.go

@@ -771,3 +771,26 @@ func TestSquashCommitMessage(t *testing.T) {
 	require.Nil(t, err)
 	require.Equal(t, "", commitMessage)
 }
+
+func TestExtractMessageOverride(t *testing.T) {
+	_, ok := extractMessageOverride("no override here")
+	assert.False(t, ok, "found unexpected message override")
+
+	_, ok = extractMessageOverride("==COMITT_MSG==\r\nUnclosed message")
+	assert.False(t, ok, "found unexpected message override")
+
+	msg, ok := extractMessageOverride("==COMMIT_MSG==\r\nThe real message\r\n==COMMIT_MSG==")
+	if assert.True(t, ok, "override was not found") {
+		assert.Equal(t, "The real message", msg)
+	}
+
+	msg, ok = extractMessageOverride("==COMMIT_MSG== \r\nThe real message\r\n  ==COMMIT_MSG==")
+	if assert.True(t, ok, "override was not found") {
+		assert.Equal(t, "The real message", msg)
+	}
+
+	msg, ok = extractMessageOverride("==SQUASH_MSG==\nThe real message\n==SQUASH_MSG==")
+	if assert.True(t, ok, "override was not found") {
+		assert.Equal(t, "The real message", msg)
+	}
+}