Make editor detect external changes to open tabs in the currently open Sketch

[Lorandil]

Sometimes a source fiIe that is open in the Arduino IDE becomes modified
from an external program (e.g. an alternate text editor like notepad++, or a
bitmap in a header file which was converted to hex by tools like image2cpp).
Because the Arduino IDE doesn't detect these modifications, it is required to
close and reopen the sketch or else changes might get lost.

I would like the IDE to detect the file change and ask what to do (like in notepad++).
This feature would help beginners, because it is frustrating if changes are ignored or
become lost.

There might even be a setting to automatically open the changed file (which will
become tricky, if there are unsaved changes).

[ubidefeo]

or a bitmap in a header file which was converted to hex by tools like image2cpp

that's how you sold it to me :)

[ag88]

in eclipse to 'add missing files' or to get the workspace project updated, it is pressing F5 (refresh), i'm not sure how easy or difficult to implement similar

[ubidefeo]

relates to #284

[per1234]

The description of the IDE's current behavior provided here seems either incorrect (outdated?) or misleading to me. Here is the current behavior:

If the sketch is in a saved state (which it will always be if the "Auto Save" setting is enabled), all external changes to the sketch files are immediately loaded automatically.

If the sketch is in an unsaved state and there have been external changes, the IDE asks the user if they would like to overwrite on save:

---

This is different from the behavior of Notepad++, which prompts on external changes rather than loading them automatically:

However, the IDE's behavior does align fairly closely with the VS Code behavior, so it's not as though the IDE's current behavior is unusual.

[per1234]

As I explained in my previous comment, Arduino IDE already has this behavior so I will close this as resolved. If anyone finds that external changes to a saved sketch file are not reflected in the Arduino IDE editor when using the latest nightly build of Arduino IDE, then please submit a new bug report and we will investigate it.