Improve issue autolinks (#6273)

* Improve issue autolinks

Update autolinks to match what github does here:

Issue in same repo: #1
Issue in different repo: org/repo#1

Fixes #6264

* Use setting.AppURL when parsing URL

Using setting.AppURL here is a more reliable way of parsing the current
URL and what other functions in this file seem to use.

* Make ComposeMetas always return a valid context

* Add per repository markdown renderers for better context

* Update for use of context metas

Now that we include the user and repo name inside context metas, update
various code and tests for this new logic

2 files changed, 21 insertions, 3 deletions

diff --git a/routers/api/v1/api.go b/routers/api/v1/api.go
index 02c74e5056..4194d98db8 100644
--- a/routers/api/v1/api.go
+++ b/routers/api/v1/api.go
@@ -584,6 +584,8 @@ func RegisterRoutes(m *macaron.Macaron) {
 						Patch(reqToken(), reqRepoWriter(models.UnitTypeIssues, models.UnitTypePullRequests), bind(api.EditLabelOption{}), repo.EditLabel).
 						Delete(reqToken(), reqRepoWriter(models.UnitTypeIssues, models.UnitTypePullRequests), repo.DeleteLabel)
 				})
+				m.Post("/markdown", bind(api.MarkdownOption{}), misc.Markdown)
+				m.Post("/markdown/raw", misc.MarkdownRaw)
 				m.Group("/milestones", func() {
 					m.Combo("").Get(repo.ListMilestones).
 						Post(reqToken(), reqRepoWriter(models.UnitTypeIssues, models.UnitTypePullRequests), bind(api.CreateMilestoneOption{}), repo.CreateMilestone)
diff --git a/routers/api/v1/misc/markdown.go b/routers/api/v1/misc/markdown.go
index 633dff98eb..9ae7a6c58c 100644
--- a/routers/api/v1/misc/markdown.go
+++ b/routers/api/v1/misc/markdown.go
@@ -5,12 +5,16 @@
 package misc
 
 import (
+	"strings"
+
 	api "code.gitea.io/sdk/gitea"
 
 	"code.gitea.io/gitea/modules/context"
 	"code.gitea.io/gitea/modules/markup/markdown"
 	"code.gitea.io/gitea/modules/setting"
 	"code.gitea.io/gitea/modules/util"
+
+	"mvdan.cc/xurls/v2"
 )
 
 // Markdown render markdown document to HTML
@@ -45,11 +49,23 @@ func Markdown(ctx *context.APIContext, form api.MarkdownOption) {
 	switch form.Mode {
 	case "gfm":
 		md := []byte(form.Text)
-		context := util.URLJoin(setting.AppURL, form.Context)
+		urlPrefix := form.Context
+		var meta map[string]string
+		if !strings.HasPrefix(setting.AppSubURL+"/", urlPrefix) {
+			// check if urlPrefix is already set to a URL
+			linkRegex, _ := xurls.StrictMatchingScheme("https?://")
+			m := linkRegex.FindStringIndex(urlPrefix)
+			if m == nil {
+				urlPrefix = util.URLJoin(setting.AppURL, form.Context)
+			}
+		}
+		if ctx.Repo != nil && ctx.Repo.Repository != nil {
+			meta = ctx.Repo.Repository.ComposeMetas()
+		}
 		if form.Wiki {
-			ctx.Write([]byte(markdown.RenderWiki(md, context, nil)))
+			ctx.Write([]byte(markdown.RenderWiki(md, urlPrefix, meta)))
 		} else {
-			ctx.Write(markdown.Render(md, context, nil))
+			ctx.Write(markdown.Render(md, urlPrefix, meta))
 		}
 	default:
 		ctx.Write(markdown.RenderRaw([]byte(form.Text), "", false))