added comment about always flag + cue fmt

Signed-off-by: Sam Alba <sam.alba@gmail.com>

dagger/pipeline.go

@@ -386,6 +386,8 @@ func (p *Pipeline) Exec(ctx context.Context, op *compiler.Value, st llb.State) (
 
 	// always?
 	if cmd.Always {
+		// FIXME: also disables persistent cache directories
+		// There's an ongoing proposal that would fix this: https://github.com/moby/buildkit/issues/1213
 		opts = append(opts, llb.IgnoreCache)
 	}
 	// mounts

stdlib/dagger/op/op.cue

@@ -45,6 +45,7 @@ package op
 	do: "exec"
 	args: [...string]
 	env?: [string]: string
+	// `true` means also ignoring the mount cache volumes
 	always?: true | *false
 	dir:     string | *"/"
 	mount: [string]: "tmpfs" | "cache" | {from: _, path: string | *"/"}

tests/compute/success/exec-nocache/main.cue

@@ -1,23 +1,23 @@
 package main
 
 import (
-    "dagger.io/alpine"
-    "dagger.io/dagger/op"
+	"dagger.io/alpine"
+	"dagger.io/dagger/op"
 )
 
 rand: {
-    string
+	string
 
-    #up: [
-        op.#Load & {from: alpine.#Image},
-        op.#Exec & {
-                always: true
-				args: ["sh", "-c", """
-					tr -dc A-Za-z0-9 </dev/urandom | head -c 13 > /id
-					"""]
-        },
-        op.#Export & {source: "/id"},
-    ]
+	#up: [
+		op.#Load & {from: alpine.#Image},
+		op.#Exec & {
+			always: true
+			args: ["sh", "-c", """
+				tr -dc A-Za-z0-9 </dev/urandom | head -c 13 > /id
+				"""]
+		},
+		op.#Export & {source: "/id"},
+	]
 }
 
 // If rand is executed twice, cue won't validate