The sketch cache might be empty, when trying to generate
the secrets include in the main sketch file from the
`secrets` property.
Closes#1999
Signed-off-by: Akos Kitta <a.kitta@arduino.cc>
* improve push/pull process
* improved diff tree performance generation
* skip some files to be synced
Co-authored-by: Francesco Stasi <f.stasi@me.com>