1 files changed, 38 insertions, 0 deletions
diff --git a/cmd/git-extract-issue/main.go b/cmd/git-extract-issue/main.go
new file mode 100644
index 0000000..4681d4d
--- /dev/null
+++ b/cmd/git-extract-issue/main.go
@@ -0,0 +1,38 @@
+package main
+
+import (
+	"fmt"
+	"os"
+	"regexp"
+)
+
+func main() {
+	argv := os.Args
+	argc := len(argv)
+	if argc != 2 {
+		return
+	}
+	branchName := argv[1]
+	fmt.Println(extractIssueNumberFromBranchName(branchName))
+}
+
+// * 123                       => #123
+// * 123-suffix                => #123
+// * feature/123               => #123
+// * feature/123-suffix        => #123
+// * feature/prefix-123        => prefix-123
+// * feature/prefix-123-suffix => prefix-123
+func extractIssueNumberFromBranchName(branchName string) string {
+	pattern := regexp.MustCompile(`\A(?:\w+/)?(\w+-)?(\d+)(?:-\w+)*\z`)
+	matches := pattern.FindSubmatch([]byte(branchName))
+	if len(matches) != 3 {
+		return ""
+	}
+	var prefix string
+	if len(matches[1]) == 0 {
+		prefix = "#"
+	} else {
+		prefix = string(matches[1])
+	}
+	return prefix + string(matches[2])
+}