An example scenario

There's path/to/java/code/Foo.java and your Android.mk has $(shell find path/to/java/code -name '*.java')

• If you do nothing in path/to/java/code, the timestamp of path/to/java/code won't be changed so kati won't run the find command.
• If you add path/to/java/code/Foo.java~ (a backup file of emacs), kati runs the find command. As there's no difference in the result of find command, kati won't re-generate build.ninja.
• If you add path/to/java/code/Bar.java, kati runs the find command and re-generate build.ninja.