Append `(comment)` when a link points at a comment rather than the whole issue (#23734)

Close #23671 

For the feature mentioned above, this PR append ' (comment)' to the
rendered html if it is a hashcomment.
After the PR, type in the following

```
pull request from other repo:
http://localhost:3000/testOrg/testOrgRepo/pulls/2

pull request from this repo:
http://localhost:3000/aaa/testA/pulls/2

issue comment from this repo:
http://localhost:3000/aaa/testA/issues/1#issuecomment-18

http://localhost:3000/aaa/testA/pulls/2#issue-9

issue comment from other repo:
http://localhost:3000/testOrg/testOrgRepo/pulls/2#issuecomment-24

http://localhost:3000/testOrg/testOrgRepo/pulls/2#issue
```
Gives:
<img width="687" alt="截屏2023-03-27 13 53 06"
src="https://user-images.githubusercontent.com/17645053/227852387-2b218e0d-3468-4d90-ad81-d702ddd17fd2.png">



Other than the above feature, this PR also includes two other changes:

1 Right now, the render of links from file changed tab in pull request
might not be very proper, for example, if type in the following. (not
sure if this is an issue or design, if not an issue, I will revert the
changes). example on
[try.gitea.io](https://try.gitea.io/HesterG/testrepo/pulls/1)
```
https://try.gitea.io/HesterG/testrepo/pulls/1/files#issuecomment-162725
https://try.gitea.io/HesterG/testrepo/pulls/1/files
```
it will render the following 
<img width="899" alt="截屏2023-03-24 15 41 37"
src="https://user-images.githubusercontent.com/17645053/227456117-5eccedb7-9118-4540-929d-aee9a76de852.png">

In this PR, skip processing the link into a ref issue if it is a link
from files changed tab in pull request

After:
type in following
```
hash comment on files changed tab:
http://localhost:3000/testOrg/testOrgRepo/pulls/2/files#issuecomment-24

files changed link:
http://localhost:3000/testOrg/testOrgRepo/pulls/2/files
```
Gives

<img width="708" alt="截屏2023-03-27 22 09 02"
src="https://user-images.githubusercontent.com/17645053/227964273-5dc06c50-3713-489c-b05d-d95367d0ab0f.png">

2 Right now, after editing the comment area, there will not be tippys
attached to `ref-issue`; and no tippy attached on preview as well.
example:

https://user-images.githubusercontent.com/17645053/227850540-5ae34e2d-b1d7-4d0d-9726-7701bf825d1f.mov

In this PR, in frontend, make sure tippy is added after editing the
comment, and to the comment on preview tab
After:

https://user-images.githubusercontent.com/17645053/227853777-06f56b4c-1148-467c-b6f7-f79418e67504.mov

4 files changed, 50 insertions, 10 deletions

diff --git a/modules/context/context.go b/modules/context/context.go
index 5876e23cc4..1eff1459a1 100644
--- a/modules/context/context.go
+++ b/modules/context/context.go
@@ -628,7 +628,9 @@ func (ctx *Context) Value(key interface{}) interface{} {
 	if key == git.RepositoryContextKey && ctx.Repo != nil {
 		return ctx.Repo.GitRepo
 	}
-
+	if key == translation.ContextKey && ctx.Locale != nil {
+		return ctx.Locale
+	}
 	return ctx.Req.Context().Value(key)
 }
 
diff --git a/modules/markup/html.go b/modules/markup/html.go
index 76fc54cf46..11888b8536 100644
--- a/modules/markup/html.go
+++ b/modules/markup/html.go
@@ -22,6 +22,7 @@ import (
 	"code.gitea.io/gitea/modules/regexplru"
 	"code.gitea.io/gitea/modules/setting"
 	"code.gitea.io/gitea/modules/templates/vars"
+	"code.gitea.io/gitea/modules/translation"
 	"code.gitea.io/gitea/modules/util"
 
 	"golang.org/x/net/html"
@@ -97,14 +98,30 @@ var issueFullPattern *regexp.Regexp
 // Once for to prevent races
 var issueFullPatternOnce sync.Once
 
+// regexp for full links to hash comment in pull request files changed tab
+var filesChangedFullPattern *regexp.Regexp
+
+// Once for to prevent races
+var filesChangedFullPatternOnce sync.Once
+
 func getIssueFullPattern() *regexp.Regexp {
 	issueFullPatternOnce.Do(func() {
+		// example: https://domain/org/repo/pulls/27#hash
 		issueFullPattern = regexp.MustCompile(regexp.QuoteMeta(setting.AppURL) +
 			`[\w_.-]+/[\w_.-]+/(?:issues|pulls)/((?:\w{1,10}-)?[1-9][0-9]*)([\?|#](\S+)?)?\b`)
 	})
 	return issueFullPattern
 }
 
+func getFilesChangedFullPattern() *regexp.Regexp {
+	filesChangedFullPatternOnce.Do(func() {
+		// example: https://domain/org/repo/pulls/27/files#hash
+		filesChangedFullPattern = regexp.MustCompile(regexp.QuoteMeta(setting.AppURL) +
+			`[\w_.-]+/[\w_.-]+/pulls/((?:\w{1,10}-)?[1-9][0-9]*)/files([\?|#](\S+)?)?\b`)
+	})
+	return filesChangedFullPattern
+}
+
 // CustomLinkURLSchemes allows for additional schemes to be detected when parsing links within text
 func CustomLinkURLSchemes(schemes []string) {
 	schemes = append(schemes, "http", "https")
@@ -793,15 +810,30 @@ func fullIssuePatternProcessor(ctx *RenderContext, node *html.Node) {
 	if ctx.Metas == nil {
 		return
 	}
-
 	next := node.NextSibling
 	for node != nil && node != next {
 		m := getIssueFullPattern().FindStringSubmatchIndex(node.Data)
 		if m == nil {
 			return
 		}
+
+		mDiffView := getFilesChangedFullPattern().FindStringSubmatchIndex(node.Data)
+		// leave it as it is if the link is from "Files Changed" tab in PR Diff View https://domain/org/repo/pulls/27/files
+		if mDiffView != nil {
+			return
+		}
+
 		link := node.Data[m[0]:m[1]]
-		id := "#" + node.Data[m[2]:m[3]]
+		text := "#" + node.Data[m[2]:m[3]]
+		// if m[4] and m[5] is not -1, then link is to a comment
+		// indicate that in the text by appending (comment)
+		if m[4] != -1 && m[5] != -1 {
+			if locale, ok := ctx.Ctx.Value(translation.ContextKey).(translation.Locale); ok {
+				text += " " + locale.Tr("repo.from_comment")
+			} else {
+				text += " (comment)"
+			}
+		}
 
 		// extract repo and org name from matched link like
 		// http://localhost:3000/gituser/myrepo/issues/1
@@ -810,12 +842,10 @@ func fullIssuePatternProcessor(ctx *RenderContext, node *html.Node) {
 		matchRepo := linkParts[len(linkParts)-3]
 
 		if matchOrg == ctx.Metas["user"] && matchRepo == ctx.Metas["repo"] {
-			// TODO if m[4]:m[5] is not nil, then link is to a comment,
-			// and we should indicate that in the text somehow
-			replaceContent(node, m[0], m[1], createLink(link, id, "ref-issue"))
+			replaceContent(node, m[0], m[1], createLink(link, text, "ref-issue"))
 		} else {
-			orgRepoID := matchOrg + "/" + matchRepo + id
-			replaceContent(node, m[0], m[1], createLink(link, orgRepoID, "ref-issue"))
+			text = matchOrg + "/" + matchRepo + text
+			replaceContent(node, m[0], m[1], createLink(link, text, "ref-issue"))
 		}
 		node = node.NextSibling.NextSibling
 	}
diff --git a/modules/markup/html_internal_test.go b/modules/markup/html_internal_test.go
index a048f1f527..7e04b03531 100644
--- a/modules/markup/html_internal_test.go
+++ b/modules/markup/html_internal_test.go
@@ -330,13 +330,17 @@ func TestRender_FullIssueURLs(t *testing.T) {
 	test("Look here http://localhost:3000/person/repo/issues/4",
 		`Look here <a href="http://localhost:3000/person/repo/issues/4" class="ref-issue">person/repo#4</a>`)
 	test("http://localhost:3000/person/repo/issues/4#issuecomment-1234",
-		`<a href="http://localhost:3000/person/repo/issues/4#issuecomment-1234" class="ref-issue">person/repo#4</a>`)
+		`<a href="http://localhost:3000/person/repo/issues/4#issuecomment-1234" class="ref-issue">person/repo#4 (comment)</a>`)
 	test("http://localhost:3000/gogits/gogs/issues/4",
 		`<a href="http://localhost:3000/gogits/gogs/issues/4" class="ref-issue">#4</a>`)
 	test("http://localhost:3000/gogits/gogs/issues/4 test",
 		`<a href="http://localhost:3000/gogits/gogs/issues/4" class="ref-issue">#4</a> test`)
 	test("http://localhost:3000/gogits/gogs/issues/4?a=1&b=2#comment-123 test",
-		`<a href="http://localhost:3000/gogits/gogs/issues/4?a=1&amp;b=2#comment-123" class="ref-issue">#4</a> test`)
+		`<a href="http://localhost:3000/gogits/gogs/issues/4?a=1&amp;b=2#comment-123" class="ref-issue">#4 (comment)</a> test`)
+	test("http://localhost:3000/testOrg/testOrgRepo/pulls/2/files#issuecomment-24",
+		"http://localhost:3000/testOrg/testOrgRepo/pulls/2/files#issuecomment-24")
+	test("http://localhost:3000/testOrg/testOrgRepo/pulls/2/files",
+		"http://localhost:3000/testOrg/testOrgRepo/pulls/2/files")
 }
 
 func TestRegExp_sha1CurrentPattern(t *testing.T) {
diff --git a/modules/translation/translation.go b/modules/translation/translation.go
index 5a1009bfa3..3165390c32 100644
--- a/modules/translation/translation.go
+++ b/modules/translation/translation.go
@@ -18,6 +18,10 @@ import (
 	"golang.org/x/text/language"
 )
 
+type contextKey struct{}
+
+var ContextKey interface{} = &contextKey{}
+
 // Locale represents an interface to translation
 type Locale interface {
 	Language() string