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/api/v1/repo/branch.go

@@ -498,6 +498,7 @@ func CreateBranchProtection(ctx *context.APIContext) {
 		DismissStaleApprovals:         form.DismissStaleApprovals,
 		RequireSignedCommits:          form.RequireSignedCommits,
 		ProtectedFilePatterns:         form.ProtectedFilePatterns,
+		UnprotectedFilePatterns:       form.UnprotectedFilePatterns,
 		BlockOnOutdatedBranch:         form.BlockOnOutdatedBranch,
 	}
 
@@ -643,6 +644,10 @@ func EditBranchProtection(ctx *context.APIContext) {
 		protectBranch.ProtectedFilePatterns = *form.ProtectedFilePatterns
 	}
 
+	if form.UnprotectedFilePatterns != nil {
+		protectBranch.UnprotectedFilePatterns = *form.UnprotectedFilePatterns
+	}
+
 	if form.BlockOnOutdatedBranch != nil {
 		protectBranch.BlockOnOutdatedBranch = *form.BlockOnOutdatedBranch
 	}