fix: remove source & target. and add branch.

[0x01toby]

• DRONE_COMMIT_SOURCE
• DRONE_COMMIT_TARGET

can not found in https://docs.drone.io/pipeline/environment/reference/

#4

[bradrydzewski]

Thanks, you are correct that these values do not exist. I think the solution would be to the following change:

	Commit struct {
		Rev     string `envconfig:"DRONE_COMMIT_SHA"`
		Before  string `envconfig:"DRONE_COMMIT_BEFORE"`
		After   string `envconfig:"DRONE_COMMIT_AFTER"`
		Ref     string `envconfig:"DRONE_COMMIT_REF"`
		Branch  string `envconfig:"DRONE_COMMIT_BRANCH"`
-		Source  string `envconfig:"DRONE_COMMIT_SOURCE"`
-		Target  string `envconfig:"DRONE_COMMIT_TARGET"`
+		Source  string `envconfig:"DRONE_SOURCE_BRANCH"`
+		Target  string `envconfig:"DRONE_TARGET_BRANCH"`

https://github.com/drone/drone-jira/blob/master/plugin/pipeline.go#L43:L44

[0x01toby]

you are right. I update it.

[tphoney]

Thanks for the fix @taorzhang