Add outdated example

README.md

@@ -630,7 +630,7 @@ less
 
 ### Portable tree command
 
-See [examples/tree.clj](https://github.com/borkdude/babashka/blob/8afb87142e0e4da8b6f912cfd7daf9c30b805ab3/examples/tree.clj).
+See [examples/tree.clj](https://github.com/borkdude/babashka/blob/master/examples/tree.clj).
 
 ``` shellsession
 $ clojure -Sdeps '{:deps {org.clojure/tools.cli {:mvn/version "0.4.2"}}}' examples/tree.clj src
@@ -650,6 +650,20 @@ src
 ...
 ```
 
+### List outdated maven dependencies
+
+See [examples/outdated.clj](https://github.com/borkdude/babashka/blob/master/examples/outdated.clj).
+
+``` shellsession
+$ cat /tmp/deps.edn
+{:deps {cheshire {:mvn/version "5.8.1"}
+        clj-http {:mvn/version "3.4.0"}}}
+
+$ examples/outdated.clj /tmp/deps.edn
+clj-http/clj-http can be upgraded from 3.4.0 to 3.10.0
+cheshire/cheshire can be upgraded from 5.8.1 to 5.9.0
+```
+
 ## Thanks
 
 - [adgoji](https://www.adgoji.com/) for financial support

examples/outdated.clj

@@ -0,0 +1,34 @@
+#!/usr/bin/env bb
+
+(require '[clojure.edn :as edn])
+(require '[clojure.java.shell :refer [sh]])
+(require '[clojure.string :as str])
+
+(def deps (-> (slurp (or (first *command-line-args*)
+                         "deps.edn"))
+              edn/read-string
+              :deps))
+(def with-release (zipmap (keys deps)
+                          (map #(assoc % :mvn/version "RELEASE")
+                               (vals deps))))
+
+(defn deps->versions [deps]
+  (let [res (sh "clojure" "-Sdeps" (str {:deps deps}) "-Stree")
+        tree (:out res)
+        lines (str/split tree #"\n")
+        top-level (remove #(str/starts-with? % " ") lines)
+        deps (map #(str/split % #" ") top-level)]
+    (reduce (fn [acc [dep version]]
+              (assoc acc dep version))
+            {}
+            deps)))
+
+(def version-map (deps->versions deps))
+(def new-version-map (deps->versions with-release))
+
+(doseq [[dep version] version-map
+        :let [new-version (get new-version-map dep)]
+        :when (not= version new-version)]
+  (println dep "can be upgraded from" version "to" new-version))
+
+;; Inspired by an idea from @seancorfield on Clojurians Slack