Fix trampoline file to work with Drip

Read the TRAMPOLINE_FILE environment variable instead of putting it
in a system property. Drip looks up pre-spun JVMs using a hash of the
command-line arguments, so putting the trampoline file in a system
property causes it to start a new spare JVM for every lein invocation.

bin/lein

@@ -255,13 +255,13 @@ else
         fi
         exec sh -c "exec $(cat $TRAMPOLINE_FILE)"
     else
+        export TRAMPOLINE_FILE
         $LEIN_JAVA_CMD \
             -client -XX:+TieredCompilation \
             $LEIN_JVM_OPTS \
             -Dfile.encoding=UTF-8 \
             -Dmaven.wagon.http.ssl.easy=false \
             -Dleiningen.original.pwd="$ORIGINAL_PWD" \
-            -Dleiningen.trampoline-file="$TRAMPOLINE_FILE" \
             -cp "$CLASSPATH" \
             clojure.main -m leiningen.core.main "$@"
 

bin/lein.bat

@@ -189,8 +189,7 @@ if "%1" == "trampoline" (goto RUN_TRAMPOLINE) else (goto RUN_NORMAL)
 set "TRAMPOLINE_FILE=%TEMP%\lein-trampoline-%RANDOM%.bat"
 %JAVA_CMD% -client %LEIN_JVM_OPTS% ^
  -Dleiningen.original.pwd="%ORIGINAL_PWD%" ^
- -Dleiningen.trampoline-file="%TRAMPOLINE_FILE%" ^
- -cp "%CLASSPATH%" clojure.main -e "(use 'leiningen.core.main)(apply -main (map str '(%*)))"
+ -cp "%CLASSPATH%" clojure.main -e "(use 'leiningen.core.main)(apply -main "%TRAMPOLINE_FILE%" (map str '(%*)))"
 
 if not exist "%TRAMPOLINE_FILE%" goto EOF
 call "%TRAMPOLINE_FILE%"

src/leiningen/trampoline.clj

@@ -9,8 +9,11 @@
 
 (def ^:dynamic *trampoline?* false)
 
+(defn- trampoline-file []
+  (System/getenv "TRAMPOLINE_FILE"))
+
 (defn- win-batch? []
-  (.endsWith (System/getProperty "leiningen.trampoline-file") ".bat"))
+  (.endsWith (trampoline-file) ".bat"))
 
 (defn- quote-arg [arg]
   (format "\"%s\"" arg))
@@ -33,10 +36,10 @@
 
 (defn write-trampoline [project forms deps]
   (let [command (trampoline-command-string project forms deps)
-        trampoline-file (System/getProperty "leiningen.trampoline-file")]
+        trampoline (trampoline-file)]
     (main/debug "Trampoline command:" command)
-    (.mkdirs (.getParentFile (io/file trampoline-file)))
-    (spit trampoline-file command)))
+    (.mkdirs (.getParentFile (io/file trampoline)))
+    (spit trampoline command)))
 
 (defn ^:higher-order trampoline
   "Run a task without nesting the project's JVM inside Leiningen's.