Support unprotected file patterns (#16395)

Fixes #16381

Note that changes to unprotected files via the web editor still cannot be pushed directly to the protected branch. I could easily add such support for edits and deletes if needed. But for adding, uploading or renaming unprotected files, it is not trivial.

* Extract & Move GetAffectedFiles to modules/git

routers/private/hook.go

@@ -343,6 +343,23 @@ func HookPreReceive(ctx *gitea_context.PrivateContext) {
 						return
 					}
 
+					// Allow commits that only touch unprotected files
+					globs := protectBranch.GetUnprotectedFilePatterns()
+					if len(globs) > 0 {
+						unprotectedFilesOnly, err := pull_service.CheckUnprotectedFiles(oldCommitID, newCommitID, globs, env, gitRepo)
+						if err != nil {
+							log.Error("Unable to check file protection for commits from %s to %s in %-v: %v", oldCommitID, newCommitID, repo, err)
+							ctx.JSON(http.StatusInternalServerError, private.Response{
+								Err: fmt.Sprintf("Unable to check file protection for commits from %s to %s: %v", oldCommitID, newCommitID, err),
+							})
+							return
+						}
+						if unprotectedFilesOnly {
+							// Commit only touches unprotected files, this is allowed
+							continue
+						}
+					}
+
 					// Or we're simply not able to push to this protected branch
 					log.Warn("Forbidden: User %d is not allowed to push to protected branch: %s in %-v", opts.UserID, branchName, repo)
 					ctx.JSON(http.StatusForbidden, private.Response{