internal/lsp/source: small fixes to directory filters

Add missing newlines in documentation, and allow trailing slashes in the
filter expressions.

Change-Id: I90106b209222d8cc542e3517c6ff6edb2569243d
Reviewed-on: https://go-review.googlesource.com/c/tools/+/308453
Trust: Heschi Kreinick <heschi@google.com>
Run-TryBot: Heschi Kreinick <heschi@google.com>
gopls-CI: kokoro <noreply+kokoro@google.com>
TryBot-Result: Go Bot <gobot@golang.org>
Reviewed-by: Robert Findley <rfindley@google.com>

gopls/doc/settings.md

@@ -63,8 +63,11 @@ the last filter that applies to a path controls whether it is included.
 The path prefix can be empty, so an initial `-` excludes everything.
 
 Examples:
+
 Exclude node_modules: `-node_modules`
+
 Include only project_a: `-` (exclude everything), `+project_a`
+
 Include only project_a, but not node_modules inside it: `-`, `+project_a`, `-project_a/node_modules`
 
 Default: `[]`.

internal/lsp/source/options.go

@@ -213,8 +213,11 @@ type BuildOptions struct {
 	// The path prefix can be empty, so an initial `-` excludes everything.
 	//
 	// Examples:
+	//
 	// Exclude node_modules: `-node_modules`
+	//
 	// Include only project_a: `-` (exclude everything), `+project_a`
+	//
 	// Include only project_a, but not node_modules inside it: `-`, `+project_a`, `-project_a/node_modules`
 	DirectoryFilters []string
 
@@ -747,7 +750,7 @@ func (o *Options) set(name string, value interface{}, seen map[string]struct{})
 				result.errorf("invalid filter %q, must start with + or -", filter)
 				return result
 			}
-			filters = append(filters, filepath.FromSlash(filter))
+			filters = append(filters, strings.TrimRight(filepath.FromSlash(filter), "/"))
 		}
 		o.DirectoryFilters = filters
 	case "completionDocumentation":