Configurable close and reopen keywords for PRs (#8120)

* Add settings for CloseKeywords and ReopenKeywords

* Fix and improve tests

* Use sync.Once() for initialization

* Fix unintended exported function

modules/setting/repository.go

@@ -59,6 +59,8 @@ var (
 		// Pull request settings
 		PullRequest struct {
 			WorkInProgressPrefixes []string
+			CloseKeywords          []string
+			ReopenKeywords         []string
 		} `ini:"repository.pull-request"`
 
 		// Issue Setting
@@ -122,8 +124,14 @@ var (
 		// Pull request settings
 		PullRequest: struct {
 			WorkInProgressPrefixes []string
+			CloseKeywords          []string
+			ReopenKeywords         []string
 		}{
 			WorkInProgressPrefixes: []string{"WIP:", "[WIP]"},
+			// Same as GitHub. See
+			// https://help.github.com/articles/closing-issues-via-commit-messages
+			CloseKeywords:  strings.Split("close,closes,closed,fix,fixes,fixed,resolve,resolves,resolved", ","),
+			ReopenKeywords: strings.Split("reopen,reopens,reopened", ","),
 		},
 
 		// Issue settings