docs: stop using (with-label) for cache busting

this was always a decision of convenience, doesn't make sense when
they're more useful as image metadata, which shouldn't bust caches

demos/hello.bass

@@ -1,5 +1,5 @@
 (defn main [lines]
   (-> ($ sh -c "for i in $(seq 1 $0); do echo line $i; sleep 0.5; done" $lines)
-      (with-label :start (now 0))
+      (with-env {:START (now 0)})
       (with-image (linux/alpine))
       run))

demos/multi-fail.bass

@@ -1,7 +1,9 @@
 (defn echo-sleep-exit [msg seconds exit-code]
   (subpath
     (from (linux/alpine)
-      (with-label ($ sleep (str seconds)) :at (now 0))
+      (with-env
+        ($ sleep (str seconds))
+        {:AT (now 0)})
       ($ sh -c (str "echo \"$0\"; exit " exit-code) $msg))
     ./))
 

demos/speedtest.bass

@@ -8,7 +8,7 @@
 (defn speedtest []
   (from (speedtest-cli)
     (-> ($ speedtest --accept-license --format json-pretty)
-        (with-label :at (now 0)))))
+        (with-env {:NOW (now 0)}))))
 
 (defn main []
   (let [results (next (read (speedtest) :json))]

docs/lit/guide.lit

@@ -59,20 +59,20 @@ for common tasks. If you'd like to learn the language, see \reference{bassics}.
       Thunks are cached forever. They can be cleared with \code{bass --prune},
       but this should only be necessary for regaining disk space.
     }{
-      To influence caching, use \b{with-label} to stamp thunks with arbitrary
-      data. Two thunks that differ only in labels will be cached independently.
+      If you want to run a cache multiple times, just set a random value as an
+      environment variable:
     }{{{
-      (run (with-label
+      (run (with-env
              (from (linux/alpine)
-               ($ echo "Hello, world!"))
-             :foo "bar"))
+               ($ echo "Hi again!"))
+             {:NOW (now 0)}))
     }}}{
       Tip: to avoid deep nesting like above, consider the alternative \b{->}
       form.
     }{{{
-      (-> ($ echo "Hello, world!")
+      (-> ($ echo "Hi again!")
           (with-image (linux/alpine))
-          (with-label :foo "bar")
+          (with-env {:NOW (now 0)})
           run)
     }}}
   }
@@ -181,8 +181,8 @@ for common tasks. If you'd like to learn the language, see \reference{bassics}.
 
       (defn counter [tag]
         (from (linux/alpine)
-          (-> ($ sh -c "echo x >> /var/cache/file; cat /var/cache/file | wc -l")
-              (with-label :tag tag)
+          (-> ($ sh -c "echo $0 >> /var/cache/file; cat /var/cache/file | wc -l"
+                 $tag)
               (with-mount my-cache /var/cache/))))
 
       (defn count [tag]

docs/lit/index.lit

@@ -81,7 +81,7 @@ release}{https://github.com/vito/bass/releases/latest} and skim the
   (defn ls-remote [repo ref & timestamp]
     (-> ($ git ls-remote $repo $ref)
         (with-image *git-image*)
-        (with-label :at (now 60)) ; rerun every minute
+        (with-env {:MINUTE (now 60)}) ; rerun every minute
         (read :unix-table) ; line and space separated table output
         next    ; first row   : <ref> <sha>
         first)) ; first column: <ref>

pkg/bass/ground.go

@@ -701,7 +701,8 @@ func init() {
 	Ground.Set("with-label",
 		Func("with-label", "[thunk name val]", (Thunk).WithLabel),
 		`returns thunk with the label set to val`,
-		`Labels are typically used to control caching. Two thunks that differ only in labels will evaluate separately and produce independent results.`,
+		`Labels are used to set metadata on a thunk, and are not used by the thunk itself.`,
+		`When the thunk is exported or published, labels will be included in the OCI image.`,
 		`=> (with-label ($ sleep 10) :at (now 10))`)
 
 	Ground.Set("with-port",

pkg/runtimes/testdata/sleep.bass

@@ -1 +1,3 @@
-(run (-> ($ sleep "999") (with-label :now (now 1)) (with-image (linux/alpine))))
+(run (-> ($ sleep "999")
+         (with-env {:RANDOM (str *random*)})
+         (with-image (linux/alpine))))

std/git.bass

@@ -14,7 +14,7 @@
   (defn ls-remote [repo ref & timestamp]
     (-> ($ git ls-remote $repo $ref)
         (with-image *git-image*)
-        (with-label :at (if (empty? timestamp) (now 0) (first timestamp)))
+        (with-env {:TIME (if (empty? timestamp) (now 0) (first timestamp))})
         (read :unix-table)
         next
         first))