git-codereview: allow _content to not warn

Fixes golang/go#45734

Change-Id: I20ebc9fb728c5e91a3d71d3a6290ccf27ceb14cf
Reviewed-on: https://go-review.googlesource.com/c/review/+/496775
Run-TryBot: Dmitri Shuralyov <dmitshur@golang.org>
TryBot-Result: Gopher Robot <gobot@golang.org>
Auto-Submit: Dmitri Shuralyov <dmitshur@golang.org>
Reviewed-by: Heschi Kreinick <heschi@google.com>
Reviewed-by: Dmitri Shuralyov <dmitshur@google.com>
Reviewed-by: Dmitri Shuralyov <dmitshur@golang.org>
diff --git a/git-codereview/change.go b/git-codereview/change.go
index 3bdcd75..65f503f 100644
--- a/git-codereview/change.go
+++ b/git-codereview/change.go
@@ -256,7 +256,7 @@
 	return m[1], m[2], true
 }
 
-var messageRE = regexp.MustCompile(`^(\[[a-zA-Z0-9.-]+\] )?[a-zA-Z0-9-/,. ]+: `)
+var messageRE = regexp.MustCompile(`^(\[[a-zA-Z0-9.-]+\] )?[a-zA-Z0-9-_/,. ]+: `)
 
 func commitMessageOK() bool {
 	body := cmdOutput("git", "log", "--format=format:%B", "-n", "1")
diff --git a/git-codereview/change_test.go b/git-codereview/change_test.go
index cd0cbcc..500ae69 100644
--- a/git-codereview/change_test.go
+++ b/git-codereview/change_test.go
@@ -80,6 +80,7 @@
 		{"math/rand: make randomer", true},
 		{"math/rand, crypto/rand: fix random sources", true},
 		{"cmd/internal/rsc.io/x86: update from external repo", true},
+		{"_content/blog: fix typos", true},
 	} {
 		got := messageRE.MatchString(c.in)
 		if got != c.want {