[API] generalize list header (#16551)

* Add info about list endpoints to CONTRIBUTING.md

* Let all list endpoints return X-Total-Count header 

* Add TODOs for GetCombinedCommitStatusByRef

* Fix models/issue_stopwatch.go

* Rrefactor models.ListDeployKeys

* Introduce helper func and use them for SetLinkHeader related func

1 files changed, 11 insertions, 2 deletions

diff --git a/models/issue_comment.go b/models/issue_comment.go
index 755041efd7..06b74dff85 100644
--- a/models/issue_comment.go
+++ b/models/issue_comment.go
@@ -999,7 +999,7 @@ func (opts *FindCommentsOptions) toConds() builder.Cond {
 	return cond
 }
 
-func findComments(e Engine, opts FindCommentsOptions) ([]*Comment, error) {
+func findComments(e Engine, opts *FindCommentsOptions) ([]*Comment, error) {
 	comments := make([]*Comment, 0, 10)
 	sess := e.Where(opts.toConds())
 	if opts.RepoID > 0 {
@@ -1019,10 +1019,19 @@ func findComments(e Engine, opts FindCommentsOptions) ([]*Comment, error) {
 }
 
 // FindComments returns all comments according options
-func FindComments(opts FindCommentsOptions) ([]*Comment, error) {
+func FindComments(opts *FindCommentsOptions) ([]*Comment, error) {
 	return findComments(x, opts)
 }
 
+// CountComments count all comments according options by ignoring pagination
+func CountComments(opts *FindCommentsOptions) (int64, error) {
+	sess := x.Where(opts.toConds())
+	if opts.RepoID > 0 {
+		sess.Join("INNER", "issue", "issue.id = comment.issue_id")
+	}
+	return sess.Count(&Comment{})
+}
+
 // UpdateComment updates information of comment.
 func UpdateComment(c *Comment, doer *User) error {
 	sess := x.NewSession()