enhance(api): add GitHub-compatible /repos/{owner}/{repo}/commits/{ref} endpoint (#38770)

Gitea currently exposes the endpoint:
 
`GET /repos/{owner}/{repo}/git/commits/{sha}`
 
to retrieve a single commit. However, GitHub provides the equivalent
endpoint as:
 
`GET /repos/{owner}/{repo}/commits/{ref}`
 
Applications integrating with both GitHub and Gitea must implement
platform-specific logic to use different endpoints, reducing API
compatibility.
 
Fixes #38225

---------

Co-authored-by: wxiaoguang <wxiaoguang@gmail.com>
Co-authored-by: Giteabot <teabot@gitea.io>

routers/api/v1/api.go

@@ -1484,7 +1484,11 @@ func Routes() *web.Router {
 						Post(reqToken(), reqRepoWriter(unit.TypeCode), bind(api.CreateStatusOption{}), repo.NewCommitStatus)
 				}, reqRepoReader(unit.TypeCode))
 				m.Group("/commits", func() {
-					m.Get("", context.ReferencesGitRepo(), repo.GetAllCommits)
+					m.Group("", func() {
+						m.Get("", repo.GetAllCommits)
+						m.Get("/{sha}", repo.GetSingleCommit) // GitHub-compatible endpoint
+						m.Get("/{sha}.{diffType:diff|patch}", repo.DownloadCommitDiffOrPatch)
+					}, context.ReferencesGitRepo(true))
 					m.PathGroup("/*", func(g *web.RouterPathGroup) {
 						// Mis-configured reverse proxy might decode the `%2F` to slash ahead, so we need to support both formats (escaped, unescaped) here.
 						// It also matches GitHub's behavior

routers/api/v1/repo/commits.go

@@ -24,7 +24,7 @@ import (
 func GetSingleCommit(ctx *context.APIContext) {
 	// swagger:operation GET /repos/{owner}/{repo}/git/commits/{sha} repository repoGetSingleCommit
 	// ---
-	// summary: Get a single commit from a repository
+	// summary: Get a single commit from a repository, it has a GitHub-compatible alias "/repos/{owner}/{repo}/commits/{ref}"
 	// produces:
 	// - application/json
 	// parameters: