Show correct text when comparing commits on empty pull request (#16569)

* fix

* use own text

* Update templates/repo/commits_table.tmpl

Co-authored-by: marty <m.karkossa@ultraware.nl>
Co-authored-by: zeripath <art27@cantab.net>

options/locale/locale_en-US.ini

@@ -1040,6 +1040,7 @@ editor.require_signed_commit = Branch requires a signed commit
 commits.desc = Browse source code change history.
 commits.commits = Commits
 commits.no_commits = No commits in common. '%s' and '%s' have entirely different histories.
+commits.nothing_to_compare = These branches are equal.
 commits.search = Search commits…
 commits.search.tooltip = You can prefix keywords with "author:", "committer:", "after:", or "before:", e.g. "revert author:Alice before:2019-04-01".
 commits.find = Search

routers/web/repo/pull.go

@@ -527,6 +527,10 @@ func PrepareViewPullInfo(ctx *context.Context, issue *models.Issue) *git.Compare
 		return nil
 	}
 
+	if compareInfo.HeadCommitID == compareInfo.MergeBase {
+		ctx.Data["IsNothingToCompare"] = true
+	}
+
 	ctx.Data["PullRequestWorkInProgressPrefixes"] = setting.Repository.PullRequest.WorkInProgressPrefixes
 
 	if pull.IsWorkInProgress() {

templates/repo/commits_table.tmpl

@@ -2,6 +2,9 @@
 	<div class="commits-table-left df ac">
 		{{if or .PageIsCommits (gt .CommitCount 0)}}
 			{{.CommitCount}} {{.i18n.Tr "repo.commits.commits"}} {{if .Branch}}({{.Branch}}){{end}}
+		{{else if .IsNothingToCompare }}
+			{{.i18n.Tr "repo.commits.nothing_to_compare" }} {{if .Branch}}({{.Branch}}){{end}}
+
 		{{else}}
 			{{.i18n.Tr "repo.commits.no_commits" $.BaseBranch $.HeadBranch }} {{if .Branch}}({{.Branch}}){{end}}
 		{{end}}