Best way to "hack" a library without forking it

Question

I'm using Visual Studio Code and PlatformIO. I added some libraries to my project using platformio.ini:

lib_deps = 
 olikraus/U8g2@^2.34.4
 crankyoldgit/IRremoteESP8266@^2.8.4
 plerup/EspSoftwareSerial@^6.16.1
 rlogiacco/CircularBuffer@^1.3.3
 https://github.com/me-no-dev/ESPAsyncWebServer.git
 makuna/NeoPixelBus@^2.7.0
 adafruit/Adafruit BusIO@^1.13.2
 bblanchon/ArduinoJson@^6.19.4
 adafruit/Adafruit PN532@^1.2.2
 khoih-prog/ESPAsync_WiFiManager@^1.15.1
 https://github.com/guestisp/ESP32AsyncDNSServer.git

Now, let's say I have to "hack" few lines of code inside a library to fit my needs. Since it's a very specific change (not something that can be useful to others) I can easily change directly the source code without forking it on github.

The downside is every time I download again the libraries (or set up another dev machine) I lose all my changes.

I can also move the downloaded library to the lib/ subfolder in the project tree, removing the dependency from lib_deps.

I wonder if there is a more reliable way to do this, i.e. applying a patch after downloading the code (yocto-like).

Answer 1

Use a local source control and repository of your choice. Obtain the latest published rev of the library and make your changes to it (I assume you have already done this, probably a number of times). Check in your changed revision of the library to your local repository. When a new rev becomes available, obtain it and merge it into your local repository.

Update:

One problem of this approach is I will end up with nested repositories.

I'm coming from old-school source control - file management. rcs, in my case (don't laugh). I'm guessing your local modifications affect only one or a few of the library files. Mightn't something that simple - a file-level merge - solve your issue (regardless of which tool you choose to do it)?

• Mark: One problem of this approach is I will end up with nested repositories. My project directory is already a git repository. If I clone the library repository inside, say, the lib folder it won't pushed inside mine since it's nested. At least, I was not able to do this.
• Edgar Bonet: @Mark: You may clone the library outside of your project's directory, commit your changes there in a dedicated branch, and then include it into your project as a git submodule. Alternatively, you may consider using a git subtree.
• Mark: @EdgarBonet yep, git subtree did the trick (and for me is the actual solution to my question). I only knew git submodules that are tricky for this kind of scenario.