CMake: Generate scmrev.h at build time instead of configure time.

[AdmiralCurtiss]

This avoids the reconfigure every time your git HEAD changes. It should also detect the -dirty suffix more reliably.

[TellowKrinkle]

I feel like the proper way to do this would be with an add_custom_command(OUTPUT scmrev.h DEPENDS git files), which you then target_sources into common, so it would have proper dependency tracking and you wouldn't need the copy_if_different to avoid recompiling files for every build.

[AdmiralCurtiss]

I understand what you mean conceptually but I have no idea how that would actually look in practice. You can't exactly put a dependency on the entire .git directory.

[AdmiralCurtiss]

(Note that that wouldn't detect the -dirty flag correctly either even if you did somehow manage a dependency on everything in .git.)

[iwubcode]

I don't understand why this build would taint other PRs but my PR build fails with:

../Source/Core/Common/Version.cpp:8:10: fatal error: Common/scmrev.h: No such file or directory
8 | #include "Common/scmrev.h"

Just coincidence?

[TellowKrinkle]

You can't exactly put a dependency on the entire .git directory.

Same two files the current script uses to decide whether to rerun cmake

(Note that that wouldn't detect the -dirty flag correctly either even if you did somehow manage a dependency on everything in .git.)

True, I guess this is fine then.

Could you find git with QUIET or pass it in as an argument to the script so it doesn't print this on every build?

-- Found Git: /usr/bin/git (found version "2.39.2 (Apple Git-143)") 

[AdmiralCurtiss]

I don't understand why this build would taint other PRs but my PR build fails with:

I mean... I agree that this feels related, but I'm not really sure why this would cause this, either. Odd.

Could you find git with QUIET or pass it in as an argument to the script so it doesn't print this on every build?

Yup, I've added the git executable path to the passed parameters.