caddyhttp: Add plaintext response to `file_server browse` (#6093)

* Added plaintext support to file_server browser

This commit is twofold: First it adds a new optional
field, `return_type`, to `browser` for setting the
default format of the returned index (html, json or plaintext).
This is used when the `Accept` header is set to `/*`.

Second, it adds a preliminary `text/plain`
support to the `file_server` browser that
returns a text representation of the file
system, when an `Accept: text/plain` header
is present, with the behavior discussed above.

* Added more details and better formatting to plaintext browser

* Replaced returnType conditions with a switch statement

* Simplify

---------

Co-authored-by: Matt Holt <[email protected]>

1 files changed, 7 insertions, 5 deletions

diff --git a/modules/caddyhttp/fileserver/caddyfile.go b/modules/caddyhttp/fileserver/caddyfile.go
index 6ad9190f3..d90e4f9a0 100644
--- a/modules/caddyhttp/fileserver/caddyfile.go
+++ b/modules/caddyhttp/fileserver/caddyfile.go
@@ -113,13 +113,15 @@ func (fsrv *FileServer) UnmarshalCaddyfile(d *caddyfile.Dispenser) error {
 			fsrv.Browse = new(Browse)
 			d.Args(&fsrv.Browse.TemplateFile)
 			for nesting := d.Nesting(); d.NextBlock(nesting); {
-				if d.Val() != "reveal_symlinks" {
+				switch d.Val() {
+				case "reveal_symlinks":
+					if fsrv.Browse.RevealSymlinks {
+						return d.Err("Symlinks path reveal is already enabled")
+					}
+					fsrv.Browse.RevealSymlinks = true
+				default:
 					return d.Errf("unknown subdirective '%s'", d.Val())
 				}
-				if fsrv.Browse.RevealSymlinks {
-					return d.Err("Symlinks path reveal is already enabled")
-				}
-				fsrv.Browse.RevealSymlinks = true
 			}
 
 		case "precompressed":